westnile virus book2

The West Nile Virus Guide &

Mosquito Fact Book

Compiled, edited & published by Scott Parat

A Culex quinquefasciatus mosquito on a human finger. The Culex quinquefasciatus mosquito is proven to be a

vector associated with transmission of the West Nile Virus.

West Nile Virus --- Facts, Resources & Information

I dedicate this book to my loving wife who has endured my hours of research and constant attempts to publish this book. A book that I hope makes information regarding the west nile virus available in a concise, life changing form. You’ve endured my constant illness and have stood by. I am indeed a blessed man. Liz, I love you!

Preface I want to “thank-you” for purchasing the “West Nile Virus Guide” and hope that you’ll find it very practical and useful. My goal was to provide you with information that you need to realize that the west nile virus is a real threat and I wanted to provide you with the information you need to protect yourself and loved ones from possibly contracting this dangerous disease. If you register your copy of this ebook, I’ll keep you informed of updates, new resources and new developments pertaining to west nile virus and mosquito control. Send a blank email to [email protected] and you’ll be automatically registered. Anytime you see blue text with a line under it, chances are that it is a hyper-link, that means if you place your mouse pointer over it, you’ll be able to click on that link and if you are connected to the internet, you’ll go straight to that website. At the time of publishing this ebook all links were active. I cannot control links that belong to other people so please don’t send me an email regarding a link that’s not working… I simply can’t do anything about it. I struggled with writing an appropriate introduction to a book that is so close to my heart. So I decided to approach the chore from a practical point of view. I happen to live in a low lying area in Midwestern United States. I have a river on one end of my property and a conservation area on the other end..this area floods every spring and holds 2 to 3 feet of water. It becomes a virtual “mosquito factory”!

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mailto:[email protected]


With the advent of west nile virus, my wife and I became concerned for the health of our family. During the summer months you can literally hear the buzz sound of mosquitoes as twilight approaches. It’s currently early fall and you won’t believe this but I’m watching 2 mosquitoes hover around my desklamp. Yep, they invade the house everytime the door is open. By now you must be getting the picture. Mosquitoes plus west nile virus was a reality in our lives. It’s September and as I listen to the radio another elderly man, 78 just died from a west nile virus infection. It’s real..it’s here and you need to protect yourself. As you read you’ll find out that the virus is traveling across the United States. If it’s not in your state now..it will be! The west nile virus is not restricted to the United States. As I studied, I discovered the virus has affected much of the world. This particular book covers issues in the United States, however, the facts regarding to the virus and mosquitoes can be applied to anyplace the virus and mosquitoes are present. I hope and pray that you, your family and loved ones will be positively affected by the knowledge you gain from reading this ebook and applying the facts. To your health, Scott Parat ========================= Note: The below Table of Contents is live. You can click on either a description or page number and be taken to that page. It is a very easy way to navigate and use this book as a reference guide. This book was compiled from different US governmental agencies and is based on current research regarding the west nile virus and mosquito and their respective control.



PREFACE ..................................................................................................................................................... 2 INTRODUCTION TO THE WEST NILE VIRUS ................................................................................... 7 BACKGROUND: VIRUS HISTORY AND DISTRIBUTION................................................................. 9

HISTORY..................................................................................................................................................... 9 HUMAN CASE AND VIRUS DISTRIBUTION INFORMATION............................................................................ 9

WEST NILE VIRUS: WHAT YOU NEED TO KNOW......................................................................... 10 WHAT IS WEST NILE VIRUS? ................................................................................................................... 10 WHAT CAN I DO TO PREVENT WNV? ...................................................................................................... 10 WHAT ARE THE SYMPTOMS OF WNV?..................................................................................................... 10 HOW DOES WEST NILE VIRUS SPREAD? .................................................................................................. 10 HOW SOON DO INFECTED PEOPLE GET SICK? .......................................................................................... 11 HOW IS WNV INFECTION TREATED? ....................................................................................................... 11 WHAT SHOULD I DO IF I THINK I HAVE WNV? ....................................................................................... 11 WHAT IS THE RISK OF GETTING SICK FROM WNV? ................................................................................. 11 WHAT ELSE SHOULD I KNOW?................................................................................................................. 12

LINKS TO STATE AND LOCAL GOVERNMENT WEST NILE VIRUS WEB SITES................... 13 LIST OF STATE AND LOCAL HEALTH DEPARTMENT WEB SITES, BY STATE AND CITY HEALTH DEPARTMENT WEST NILE VIRUS WEB SITES ........................................................................................... 13 ADD.......................................................................................................................................................... 15

IT'S TIME TO PREPARE FOR WEST NILE VIRUS. ......................................................................... 16 FIVE COMMON MYTHS ABOUT WEST NILE VIRUS.................................................................................... 16 WEST NILE VIRUS TRANSMISSION CYCLE................................................................................................ 18

WHAT YOU NEED TO KNOW ABOUT MOSQUITO REPELLENT ............................................... 22 WHICH MOSQUITO REPELLENTS WORK BEST .......................................................................................... 22 UPDATED INFORMATION REGARDING INSECT REPELLENTS...................................................................... 25

VERTEBRATE ECOLOGY ..................................................................................................................... 27 BIRDS ....................................................................................................................................................... 27 DOGS AND CATS....................................................................................................................................... 27 HORSES .................................................................................................................................................... 28 OTHER VERTEBRATES .............................................................................................................................. 28

ENTOMOLOGY ........................................................................................................................................ 28 VIROLOGY: CLASSIFICATION OF WEST NILE VIRUS ................................................................................. 29 PUBLIC HEALTH CONFRONTS THE MOSQUITO: DEVELOPING SUSTAINABLE STATE AND LOCAL MOSQUITO CONTROL PROGRAMS............................................................................................................................... 30 WHAT YOU CAN DO ABOUT MOSQUITO CONTROL.................................................................................. 31

MOSQUITOES........................................................................................................................................... 33 WHAT KINDS OF MOSQUITOES ARE COMMON IN ILLINOIS? ....................................................................... 33 DO ALL MOSQUITOES CARRY DISEASE? .................................................................................................... 33 WHAT IS THE BEST WAY TO REDUCE POPULATIONS OF MOSQUITOES? ...................................................... 34 HOW CAN PEOPLE PROTECT THEMSELVES FROM MOSQUITO BITES? .......................................................... 35

MOSQUITOES AND ENCEPHALITIS .................................................................................................. 36 DISEASES.................................................................................................................................................. 36 PREVENT MOSQUITOES FROM BREEDING AROUND THE HOME................................................................. 36

West Nile Virus Guide PROTECTION FROM MOSQUITO BITES....................................................................................................... 37

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QUESTIONS AND ANSWERS ABOUT MOSQUITO PREVENTION FOR PEOPLE, PROPERTY AND PETS .................................................................................................................................................. 38

WHAT KINDS OF DISEASES CAN BE CARRIED BY MOSQUITOES?................................................................. 38 WHAT IS ENCEPHALITIS? .......................................................................................................................... 38 HOW CAN I HELP PROTECT MY FAMILY AND MYSELF FROM MOSQUITOES AND THE DISEASES THEY MAY CARRY? .................................................................................................................................................... 38

QUESTIONS AND ANSWERS ABOUT SPRAYING FOR ADULT MOSQUITOES ...................... 41 WHAT INSECTICIDES ARE USED TO FOG FOR MOSQUITOES? ...................................................................... 42 ARE THE INSECTICIDES USED FOR FOGGING SAFE?.................................................................................... 43 DO I NEED TO WASH HOME-GROWN FRUITS AND VEGETABLES AFTER THE MOSQUITO FOGGING? ............. 43 WILL THE FOGGING KILL BIRDS OR OTHER LARGE ANIMALS? ................................................................... 44

THE EPA, PESTICIDES AND MOSQUITO CONTROL..................................................................... 45 HOW ARE MOSQUITOES CONTROLLED WITH PESTICIDES AND OTHER METHODS?................................... 46 WHAT CAN I DO TO REDUCE THE NUMBER OF MOSQUITOES IN AND AROUND MY HOME? ..................... 46 THE EPA’S VIEW OF LARVICIDES FOR MOSQUITO CONTROL................................................................... 48 WHAT IS THE MOSQUITO LIFE CYCLE? .................................................................................................... 49 WHAT ARE LARVICIDES?.......................................................................................................................... 49 WHAT ARE MICROBIAL LARVICIDES? ...................................................................................................... 49

INFORMATION ON ARBOVIRAL ENCEPHALITIDES.................................................................... 53 LA CROSSE ENCEPHALITIS ....................................................................................................................... 55 EASTERN EQUINE ENCEPHALITIS.............................................................................................................. 56 WESTERN EQUINE ENCEPHALITIS............................................................................................................. 56 ST. LOUIS ENCEPHALITIS.......................................................................................................................... 57 POWASSAN ENCEPHALITIS ....................................................................................................................... 57 VENEZUELAN EQUINE ENCEPHALITIS....................................................................................................... 57 JAPANESE ENCEPHALITIS.......................................................................................................................... 58 TICK-BORNE ENCEPHALITIS..................................................................................................................... 58 WEST NILE ENCEPHALITIS ....................................................................................................................... 59

QUESTIONS AND ANSWERS ABOUT WEST NILE .......................................................................... 60 OVERVIEW OF WEST NILE VIRUS .................................................................................................... 61

CASES OF WEST NILE HUMAN DISEASE ................................................................................................... 62 UNDERSTANDING THE NUMBERS POSTED FOR WEST NILE VIRUS CASES ........................................ 63

WEST NILE VIRUS AND DEAD BIRDS ............................................................................................... 65 WHO'S AT RISK FOR WEST NILE VIRUS ......................................................................................... 65 TRANSMISSION ....................................................................................................................................... 66

WEST NILE VIRUS POLIOMYELITIS ....................................................................................................... 71 PREVENTION............................................................................................................................................. 72

INSECT REPELLENT USE AND SAFETY ........................................................................................... 74 GENERAL QUESTIONS............................................................................................................................... 74 ACTIVE INGREDIENTS (TYPES OF INSECT REPELLENT) ............................................................................. 74 USING REPELLENTS PROPERLY ................................................................................................................ 76 CHILDREN ................................................................................................................................................ 77 INSECT REPELLENTS CONTAINING DEET AND SUNSCREEN...................................................................... 78 WEST NILE VIRUS VACCINE...................................................................................................................... 79

TESTING AND TREATING WEST NILE VIRUS IN HUMANS UPDATED!................................ 80 QUESTIONS ABOUT COMMERCIAL LABORATORIES................................................................. 81



WEST NILE VIRUS, PREGNANCY AND BREAST-FEEDING ......................................................... 82 BREASTFEEDING....................................................................................................................................... 84 BLOOD TRANSFUSION, ORGAN DONATION AND BLOOD DONATION SCREENING INFORMATION .............. 85

UPDATE ON DETECTION OF WNV IN BLOOD DONATIONS -- FROM MMWR, SEPTEMBER 18, 2003........................................................................................................................................................ 85 GENERAL INFORMATION ON SCREENING OF BLOOD DONATIONS FOR WNV ................. 86 PESTICIDES USED IN MOSQUITO CONTROL................................................................................. 91 WEST NILE VIRUS AND DOGS AND CATS ....................................................................................... 93 WEST NILE VIRUS AND HORSES........................................................................................................ 94

WEST NILE VIRUS AND SQUIRRELS .......................................................................................................... 95 WEST NILE VIRUS AND WILD GAME/MEAT ............................................................................................. 96

RECOMMENDATIONS FOR PROTECTING OUTDOOR WORKERS FROM WEST NILE VIRUS EXPOSURE................................................................................................................................. 103

Recommendations for employers of Outdoor Workers ..................................................................... 103 RECOMMENDATIONS FOR WORKERS ....................................................................................................... 104

RECOMMENDATIONS FOR PROTECTING LABORATORY, FIELD, AND CLINICAL WORKERS FROM WEST NILE VIRUS EXPOSURE....................................................................... 105

Occupational Risk............................................................................................................................. 105 Recommendations for employers ...................................................................................................... 106 Recommendations for workers.......................................................................................................... 106

.......................................................................................................................................... 107 CONCLUSION



Introduction to the West Nile Virus

West Nile virus emerged in the United States in the New York metropolitan area in the fall of 1999. Since then, the virus, which can be transmitted to humans by the bite of an infected mosquito, has quickly spread across the country.

In Illinois, West Nile virus was first identified in September 2001 when laboratory tests confirmed its presence in two dead crows found in the Chicago area. The following year, the state's first human cases and deaths from West Nile disease were recorded and all but two of the state's 102 counties eventually reported a positive human, bird, mosquito or horse case. By the end of 2002, Illinois had counted more human cases (884) and deaths (67) than any other state in the nation. In 2003, the epicenter of West Nile disease moved westward. Colorado reported the highest number of cases (2,947), easily surpassing the caseload record for the mosquito-borne disease set the previous year by Illinois. The number of West Nile human cases in Illinois fell dramatically with just 54 reported and only one death. Illinois' caseload in 2004 was slightly higher than the previous year with 60 reported cases and four deaths. For the second consecutive year, the country's western states had the most cases with California leading the way with 771, followed by Arizona with 391 and Colorado with 276. In 2005, Illinois' first human cases were reported on July 29.

Most state Public Health services maintain a sophisticated disease surveillance system to monitor animals and insects that can potentially carry the virus: dead crows, robins, blue jays, mosquitoes and horses. Mosquitoes can either carry the virus or get it by feeding on infected birds. The surveillance system also includes infectious disease physicians, hospital laboratory directors and infection control practitioners, local health departments and laboratory staff, environmental health and infectious diseases divisions who test for and report suspect or confirmed cases of various diseases that can be caused by mosquito-borne viruses.

Mild cases of West Nile infections may cause a slight fever or headache. More severe infections are marked by a rapid onset of a high fever with head and body aches, disorientation, tremors, convulsions and, in the most severe cases, paralysis or death. Usually symptoms occur from three to 14 days after the bite of an infected mosquito. Persons at the highest risk for serious illness are those 50 years of age or older.

The best way to prevent West Nile encephalitis and other mosquito-borne illnesses is to reduce the number of mosquitoes around your home and neighborhood and to take personal precautions to avoid mosquito bites.


http://www.cdc.gov/ncidod/dvbid/westnile/surv&control04Maps_PrinterFriendly.htm

http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm








Background: Virus History and DistributionIntroduction

West Nile virus (WNV) has emerged in recent years in temperate regions of Europe and North America, presenting a threat to public and animal health. The most serious manifestation of WNV infection is fatal encephalitis (inflammation of the brain) in humans and horses, as well as mortality in certain domestic and wild birds. WNV has also been a significant cause of human illness in the United States in 2002 and 2003.

West Nile Virus Guide

History West Nile virus was first isolated from a febrile adult woman in the West Nile District of Uganda in 1937. The ecology was characterized in Egypt in the 1950s. The virus became recognized as a cause of severe human meningitis or encephalitis (inflammation of the spinal cord and brain) in elderly patients during an outbreak in Israel in 1957. Equine disease was first noted in Egypt and France in the early 1960s. WNV first appeared in North America in 1999, with encephalitis reported in humans and horses.The subsequent spread in the United States is an important milestone in the evolving history of this virus.

View enlarged map of

laboratory-positive West Nile virus

infections during 2003

Geographic Distribution

West Nile virus has been described in Africa, Europe, the Middle East, west and central Asia, Oceania (subtype Kunjin), and most recently, North America.

Outbreaks of WNV encephalitis in humans have occurred in Algeria in 1994, Romania in 1996-1997, the Czech Republic in 1997, the Democratic Republic of the Congo in 1998, Russia in 1999, the United States in 1999-2003, and Israel in 2000. Epizootics of disease in horses occurred in Morocco in 1996, Italy in 1998, the United States in 1999-2001, and France in 2000, and in birds in Israel in 1997-2001 and in the United States in 1999-2002.

In the U.S. since 1999, WNV human, bird, veterinary or mosquito activity have been reported from all states except Hawaii, Alaska, and Oregon.

Human Case and Virus Distribution Information • Current human case and epizootic distribution maps (on Statistics,

Surveillance, and Control page) • Case human counts for 2003


http://www.cdc.gov/ncidod/dvbid/westnile/surv&control03Maps.htm






http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount03_detailed.htm


• Human case information and maps from 2002 • From 1999 through 2001, there were 149 cases of West Nile virus human

illness in the United States reported to CDC and confirmed, including 18 deaths.

West Nile Virus: What You Need To Know

What Is West Nile Virus? West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. This fact sheet contains important information that can help you recognize and prevent West Nile virus.

What Can I Do to Prevent WNV? The easiest and best way to avoid WNV is to prevent mosquito bites.

• When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.

• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.

• Make sure you have good screens on your windows and doors to keep mosquitoes out.

• Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.

What Are the Symptoms of WNV?

• Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

• Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks.

• No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.

How Does West Nile Virus Spread? West Nile Virus Guide


http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount02.htm

http://www.cdc.gov/ncidod/dvbid/westnile/surv&control03Maps02.htm

http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm



• Infected Mosquitoes. Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.


• Transfusions, Transplants, and Mother-to-Child. In avery small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.

• Not through touching. WNV is not spread through casual contact such as touching or kissing a person with the virus.

How Soon Do Infected People Get Sick? People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito.

How Is WNV Infection Treated? There is no specific treatment for WNV infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own, although even healthy people have become sick for several weeks. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing and nursing care.

What Should I Do if I Think I Have WNV? Milder WNV illness improves on its own, and people do not necessarily need to seek medical attention for this infection though they may choose to do so. If you develop symptoms of severe WNV illness, such as unusually severe headaches or confusion, seek medical attention immediately. Severe WNV illness usually requires hospitalization. Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that could be WNV.

What Is the Risk of Getting Sick from WNV? People over 50 at higher risk to get severe illness. People over the age of 50 are more likely to develop serious symptoms of WNV if they do get sick and should take special care to avoid mosquito bites. Being outside means you're at risk. The more time you're outdoors, the more time you could be bitten by an infected mosquito. Pay attention to avoiding mosquito bites if you spend a lot of time outside, either working or playing. Risk through medical procedures is very low. All donated blood is checked for WNV before being used. The risk of getting WNV through blood transfusions and organ transplants is very small, and should not prevent people who need surgery from having it. If you have concerns, talk to your doctor. Pregnancy and nursing do not increase risk of becoming infected with WNV. The risk that WNV may present to a fetus or an infant infected through breastmilk is still being evaluated. Talk with your care provider if you have concerns.

What Is the CDC Doing About WNV? CDC is working with state and local health departments, the Food and Drug


http://mosquito-magnets.com/index.php?ref=6&affiliate_banner_id=9


Administration and other government agencies, as well as private industry, to prepare for and prevent new cases of WNV.

Some things CDC is doing include:

• Coordinating a nation-wide electronic database where states share information about WNV

• Helping states develop and carry out improved mosquito prevention and control programs

• Developing better, faster tests to detect and diagnose WNV • Creating new education tools and programs for the media, the public, and

health professionals • Opening new testing laboratories for WNV • Working with partners on the development of vaccines

What Else Should I Know? If you find a dead bird: Don't handle the body with your bare hands. Contact your local health department for instructions on reporting and disposing of the body. They may tell you to dispose fo the bird after they log your report.



Links to State and Local Government West Nile Virus Web Sites Click on a state to link directly to their West Nile virus Web page. See list below for additional city-level and main State Health Department Web sites.

Maps and boundary data are copyrighted by FOTW Flags Of The World *

• Expanded list of State and Local West Nile Virus Resources Maintained by the National Pesticide Information Center (NPIC)

List of State and Local Health Department Web Sites, by State and City Health Department West Nile Virus Web Sites

• Alabama • Alaska • Arizona • Arkansas • California

o Los Angeles County Department of Health Services • Colorado • Connecticut

o West Nile Fever Fact Sheet • Delaware • District of Columbia • Florida • Georgia

o DeKalb County Board of Health DeKalb County Mosquitoes and West Nile Home Page

• Hawaii • Idaho


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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.ct.us/dph/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dph.state.ct.us/BCH/infectiousdise/westnile.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.de.us/dhss/dph/index.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://dchealth.dc.gov/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.doh.state.fl.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.ph.dhr.state.ga.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dekalbhealth.net/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dekalbhealth.net/mosquitoes/index.html

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• Illinois • Indiana • Iowa • Kansas • Kentucky • Louisiana • Maine • Maryland • Massachusetts • Michigan • Minnesota • Mississippi • Missouri • Montana • Nebraska • Nevada • New Hampshire • New Jersey

o New Jersey Department of Agriculture West Nile Virus Information o New Jersey West Nile Virus On-line Information Resources

• New Mexico • New York

o Monroe County Department of Health Monroe County West Nile Virus page

o New York City Department of Health New York City Department of Health West Nile Virus

Information o Westchester County Department of Health

Westchester County West Nile Virus Watch • North Carolina • North Dakota • Ohio • Oklahoma • Oregon • Pennsylvania

o Philadelphia Department of Public Health Philadelphia West Nile Virus Page

• Rhode Island • South Carolina • South Dakota • Tennessee • Texas

o Harris County Public Health Services • Utah • Vermont • Virginia • Washington • West Virginia • Wisconsin • Wyoming


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.idph.state.il.us/home.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.in.us/isdh/index.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.idph.state.ia.us

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.kdhe.state.ks.us/index.html

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://publichealth.state.ky.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.oph.dhh.state.la.us/

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.michigan.gov/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.health.state.mn.us/index.html

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dphhs.state.mt.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.hhs.state.ne.us/index.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://health2k.state.nv.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dhhs.state.nh.us/DHHS/DHHS_SITE/default.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.nj.us/health/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.nj.us/agriculture/westnile.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.state.nj.us/health/lh/lincs/westnile.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.health.state.nm.us

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.ci.nyc.ny.us/html/doh/home.html

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.westchestergov.com/health/default.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.westchestergov.com/health/Westnile.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.dhhs.state.nc.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.health.state.nd.us/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.odh.state.oh.us/odh_home.html

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.healthyvermonters.info/

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.vdh.state.va.us/

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It's time to prepare for West Nile Virus.West Nile Virus is spread by mosquitoes. Infection with the virus can cause severe and sometimes fatal illness. There were over 4000 cases of West Nile disease in the US during 2002, including 284 deaths. It is likely that all mainland states in the United States will see West Nile virus activity in 2003.

To help you prepare for mosquito season, read the truth about some common West Nile virus myths:

Five Common Myths about West Nile Virus Myth #1: There's not much I can do about West Nile virus. Truth: There is a lot that you, personally, can do to reduce your chance of West Nile virus infection.


• Reduce the number of mosquito bites you get. Make a habit of using insect repellent with DEET when outdoors. Spray repellent on exposed skin and clothing. Get the details about safe repellent use.

• Prime mosquito-biting hours are usually dusk to dawn. Pay special attention to protection during these hours, or avoid being outdoors.

• You can reduce the number of mosquitoes around your home. Mosquitoes breed in standing water, so check your yard once a week: get rid of containers that aren't being used, empty water from flower pots, change water in bird baths and maintain clean gutters.

Avoid mosquito bites by applying insect repellent when spending time outdoors. Use repellent safely. Always read and follow product instructions.

• Make sure window and door screens are in good condition. Have an older neighbor or family member? See if they need help installing or repairing screens.

Myth #2: Kids are at the most danger of getting sick from West Nile virus. Truth: People over 50 are at the highest risk for developing severe West Nile disease.

• Relatively few children have been reported with severe West Nile Virus disease. By contrast, most of the deaths due to WNV during 2002 were among people over 50 years old. Half of those deaths were among people over 77 years old.


http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm

http://www.cdc.gov/ncidod/dvbid/westnile/qa/overview.htm



• It is always a good idea for children to avoid mosquito bites, but it's also important for adults - especially older adults - to take steps to avoid mosquito bites. Click here for suggestions on how to avoid mosquito bites.

Myth #3: It's only people who are already in poor health who have to worry about West Nile virus. Truth: Healthy, active older adults who spend time working and exercising outdoors have been affected by severe West Nile virus infection.

• Being over 50 is a risk factor for developing severe West Nile disease if infected with the virus. There is a risk of getting mosquito bites while leading an active life outdoors. This doesn't mean you have to stay inside - it does mean that it's important to use repellent when you go outside.

Myth #4: Repellents containing DEET are not safe. Truth: Repellents containing DEET are very safe when used according to directions.

• Because DEET is so widely used, a great deal of testing has been done. When manufacturers seek registration with the US Environmental Protection Agency (EPA) for products such as DEET, laboratory testing regarding both short-term and long-term health effects must be carried out.

• There are products with different strengths (percentage of DEET) available. The longer the protection you need the higher percent of DEET needed.

• Repellent with DEET can be used for both adults and children, according to directions

• Click here for much more information on using repellents safely.

Myth #5: As long as my area has a mosquito control program, I don't have to worry about using repellent.

Truth: Mosquito control activities don't eliminate every mosquito, so personal protection is still important.

• Public activities, such as using products to kill mosquito larvae and adult mosquitoes, are one part of control. Personal protection, such as using repellent, keeping window screens in good condition, and control of household breeding sites are other important steps.

• Collaboration between the community, the family and the individual is needed to achieve the best prevention of West Nile virus infection.


http://www.cdc.gov/ncidod/dvbid/westnile/qa/prevention.htm




West Nile Virus Transmission Cycle

• Horses infected with West Nile Virus (WNV) are not contagious. • Horses can't spread it to other horses or people. • Mosquitoes that have fed on infected birds spread WNV. • A mosquito cannot bite an infected horse and spread the virus to another horse

or person. • Horses are not known to spread West Nile Virus to people. Horses are

considered to be "dead-end" hosts for WNV because it appears that they do not develop a sufficient viremia to transmit the virus from contact. Clinical signs are usually not apparent until 3-14 days post infection and viremia. Regardless, it is very important that veterinarians and other animal health workers take standard recommended precautions for all contagious equine viral encephalitic agents such as rabies and other viral encepaphalitis agents when dealing with horses suffering from undiagnosed neurological diseases.

• Treatment consists of supportive measures, and there is no specific cure. • WNV is not analogous to Foot and Mouth Disease (FMD)) and Exotic Newcastle

Disease (END). Both FMD and END are very contagious and spread with ease and rapidity.

• There will be no quarantines nor regulatory movement restrictions placed on WNV positive horses.

• Control of WNV in horses involves working with one's veterinary practitioner to establish both effective mosquito control and vaccination programs.


http://www.cdfa.ca.gov/ahfss/ah/fmd_info.htm

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Fight The Bite! Avoid Mosquito Bites to Avoid InfectionFight The Bite! Avoid Mosquito Bites to Avoid Infection

When dealing with West Nile virus, prevention is your best bet. Fighting mosquito bites reduces your risk of getting this disease, along with others that mosquitoes can carry. Take the commonsense steps below to reduce your risk:

When dealing with West Nile virus, prevention is your best bet. Fighting mosquito bites reduces your risk of getting this disease, along with others that mosquitoes can carry. Take the commonsense steps below to reduce your risk:

• avoid bites and illness; • avoid bites and illness;

• clean out the mosquitoes from the places where you work and play; • clean out the mosquitoes from the places where you work and play;

• help your community control the disease. • help your community control the disease.

Something to remember: The chance that any one person is going to become ill from a single mosquito bite remains low. The risk of severe illness and death is highest for people over 50 years old, although people of all ages can become ill.

Something to remember: The chance that any one person is going to become ill from a single mosquito bite remains low. The risk of severe illness and death is highest for people over 50 years old, although people of all ages can become ill. Avoid Mosquito Bites

Use Insect Repellent on exposed skin when you go outdoors. Use an EPA-registered insect repellent such as those with DEET, picaridin or oil of lemon eucalyptus. Even a short time being outdoors can be long enough to get a mosquito bite. For details on when and how to apply repellent, see Insect Repellent Use and Safety in our Questions and Answers pages. See also Using Insect Repellent Safely from the EPA.

Clothing Can Help Reduce Mosquito Bites

When weather permits, wear long-sleeves, long pants and socks when outdoors. Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or another EPA-registered repellent will give extra protection. Don't apply repellents containing permethrin directly to skin. Do not spray repellent on the skin under your clothing. Get double protection: wear long

sleeves during peak mosquito biting hours, and spray repellent directly onto your clothes.

Be Aware of Peak Mosquito Hours The hours from dusk to dawn are peak biting times for many species of mosquitoes. Take extra care to use repellent and protective clothing during evening and early morning -- or consider avoiding outdoor activities during these times.



http://www.cdc.gov/ncidod/dvbid/westnile/q&a.htm

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Mosquito-Proof Your Home

Drain standing water from around your home

Drain Standing Water Mosquitoes lay their eggs in standing water.Limit the number of places around your home for mosquitoes to breed by getting rid of items that hold water. Need examples? Learn more on the Prevention of West Nile Virus Question and Answer page.

Install or Repair Screens Some mosquitoes like to come indoors. Keep them outside by having well-fitting screens on both windows and doors. Offer to help neighbors whose screens might be in bad shape.

Help Your Community

Report Dead Birds to Local Authorities Dead birds may be a sign that West Nile virus is circulating between birds and the mosquitoes in an area. Over 130 species of birds are known to have been infected with West Nile virus, though not all infected birds will die. It's important to remember that birds die from many other causes besides West Nile virus.

By reporting dead birds to state and local health departments, you can play an important role in monitoring West Nile virus. State and local agencies have different policies for collecting and testing birds, so check the Links to State and Local Government Sites page to find information about reporting dead birds in your area. Click here for more info about reporting dead birds and dealing with bird carcasses.

Mosquito Control Programs Check with local health authorities to see if there is an organized mosquito control program in your area. If no program exists, work with your local government officials to establish a program. The American Mosquito Control Association can provide advice, and their book Organization for Mosquito Control is a useful reference. The final report from the Mosquito Control Collaborative is also online.

More questions about mosquito control? A source for information about pesticides



http://www.cdc.gov/ncidod/dvbid/westnile/birdspecies.htm

http://www.cdc.gov/ncidod/dvbid/westnile/city_states.htm


http://www.cdc.gov/ncidod/dvbid/westnile/qa/wnv_birds.htm


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.mosquito.org/





and repellents is the National Pesticide Information Center, which also operates a toll-free information line: 1-800-858-7378 (check their Web site for hours).

Clean Up Mosquito breeding sites can be anywhere. Neighborhood clean up days can be organized by civic or youth organizations to pick up containers from vacant lots and parks, and to encourage people to keep their yards free of standing water. Mosquitoes don't care about fences, so it's important to control breeding sites throughout the neighborhood.

Find out more about local prevention efforts Find state and local West Nile virus information and contacts on the Links to State and Local Government Sites page.

What You Need to Know about Mosquito Repellent

Why You Should Use Mosquito Repellent

Insect repellent helps reduce your exposure to mosquito bites that may carry West Nile virus or other diseases, and allows you to continue to play, work, and enjoy the outdoors with a lower risk of disease.

When You Should Use Mosquito Repellent

Use repellent when you go outdoors. You should use repellent even if you're only going outside for a few minutes-it only takes one bite to get West Nile virus. Many of the mosquitoes that carry the West Nile virus bite between dusk and dawn. If you're outside during these hours pay special attention to using repellent.

Which Mosquito Repellents Work Best A wide variety of insect repellent products are available. CDC recommends the use of products containing active ingredients which have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing.

When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that EPA does not expect a product, when used according to the instructions label, to cause unreasonable adverse effects to human health or the environment. Of the active ingredients registered with the EPA, two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature.* Products containing


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://npic.orst.edu/




these active ingredients typically provide longer-lasting protection than others: • DEET (N,N-diethyl-m-toluamide) • Picaridin (KBR 3023) Oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)], a plant based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET. These recommendations are for domestic use in the United States. See CDC Travelers’ Health website for specific recommendations concerning protection from insects when traveling outside the United States. In addition, certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin. Permethrin is not to be used directly on skin.

How Often You Should Re-apply Repellents

Follow the directions on the product you are using. Sweating or getting wet may mean that you need to re-apply more frequently.

How the Percentage of Active Ingredient in a Product Relates to Protection Time

In general, the more active ingredient (higher percentage) it has, the longer a repellent will protect you from mosquitoes. For example, DEET products are available in many formulations--something with 30% DEET will protect you longer than one with 5% DEET. You cannot directly compare the percentage of one active ingredient to another, however. Use your common sense. Re-apply repellent if you start to get bitten and follow the label instructions. As a “rule of thumb”:

• For many hours outside (over 3-4 hours) and/or where biting is very intense—look for a repellent containing more than 20% DEET. Products with more than 50% DEET do not offer additional protection.

• For shorter periods of time, repellents containing less than 20% DEET, the repellent currently available with 7% picaridin or one of the products containing oil of lemon eucalyptus may provide adequate protection. There are other products available, but they may not protect as long as those named here.


http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=recs&obj=bugs.htm&cssNav=browseoyb



• Even if you’re going out for 10 minutes use a repellent —that’s long enough to get bitten!

Hint: Applying permethrin to your clothing ahead of time will give you even greater protection. Remember—if you’re getting bitten, do something about it! Choose a repellent that you will use consistently. Also, choose a product that will provide sufficient protection for the amount of time that you will be spending outdoors. Product labels often indicate the length of time that you can expect protection from a product. If you are concerned about using insect repellent, consult your health care provider for advice.

The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or http://npic.orst.edu.

General Considerations for Using Repellents Safely

• Always follow the instructions on the product label. • Apply repellents only to exposed skin and/or clothing (as directed on the

product label.) Do not use repellents under clothing. • Never use repellents over cuts, wounds or irritated skin. • Do not apply to eyes or mouth, and apply sparingly around ears. When using

sprays, do not spray directly on face—spray on hands first and then apply to face.

• Do not allow children to handle the product. When using on children, apply to your own hands first and then put it on the child. You may not want to apply to children’s hands.

• Use just enough repellent to cover exposed skin and/or clothing. Heavy application and saturation are generally unnecessary for effectiveness. If biting insects do not respond to a thin film of repellent, then apply a bit more.

• After returning indoors, wash treated skin with soap and water or bathe. This is particularly important when repellents are used repeatedly in a day or on consecutive days. Also, wash treated clothing before wearing it again. (This precaution may vary with different repellents—check the product label.)

• If you or your child get a rash or other bad reaction from an insect repellent, stop using the repellent, wash the repellent off with mild soap and water, and call a local poison control center for further guidance. If you go to a doctor because of the repellent, take the repellent with you to show the doctor.

Note that the label for products containing oil of lemon eucalyptus specifies that they should not to be used on children under the age of three years.

Other than those listed above, EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women, or on children.

For additional information regarding the use of repellent on children, please see CDC’s Frequently Asked Questions about Repellent Use. DEET-based repellents applied according to label instructions may be used along with


http://npic.orst.edu/



a separate sunscreen. No data are available at this time regarding the use of other active repellent ingredients in combination with a sunscreen. See http://www.epa.gov/pesticides/factsheets/insectrp.htm for additional information on using EPA-registered repellents.

In addition to wearing repellent, you can protect yourself and your family by taking these precautions:

• Wear clothing with long pants and long sleeves while outdoors. Apply permethrin or another EPA-registered repellent to clothing, as mosquitoes may bite through thin fabric. (Remember: don't use permethrin on skin.)

• Use mosquito netting over infant carriers. • Reduce the number of mosquitoes in your area by getting rid of containers

with standing water that provide breeding places for the mosquitoes.

Updated Information regarding Insect Repellents

Repellents are an important tool to assist people in protecting themselves from mosquito-borne diseases.

A wide variety of insect repellent products are available. CDC recommends the use of products containing active ingredients which have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing. EPA registration of repellent active ingredients indicates the materials have been reviewed and approved for efficacy and human safety when applied according to the instructions on the label.

Of the active ingredients registered with the EPA, two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature *. Products containing these active ingredients typically provide longer-lasting protection than others:

• DEET (N,N-diethyl-m-toluamide) • Picaridin (KBR 3023)

Oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)], a plant based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.

These recommendations are for domestic use in the United States. See CDC Travelers’ Health website for specific recommendations concerning protection from insects when traveling outside the United States.

In addition, certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this






use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin.

Length of protection from mosquito bites varies with the amount of active ingredient, ambient temperature, amount of physical activity/perspiration, any water exposure, abrasive removal, and other factors. For long duration protection use a long lasting (micro-encapsulated) formula and re-apply as necessary, according to label instructions.

EPA recommends the following precautions when using insect repellents:

• Apply repellents only to exposed skin and/or clothing (as directed on the product label.) Do not use repellents under clothing.

• Never use repellents over cuts, wounds or irritated skin. • Do not apply to eyes or mouth, and apply sparingly around ears. When using

sprays, do not spray directly on face—spray on hands first and then apply to face.

• Do not allow children to handle the product. When using on children, apply to your own hands first and then put it on the child. You may not want to apply to children’s hands.

• Use just enough repellent to cover exposed skin and/or clothing. Heavy application and saturation are generally unnecessary for effectiveness. If biting insects do not respond to a thin film of repellent, then apply a bit more.

• After returning indoors, wash treated skin with soap and water or bathe. This is particularly important when repellents are used repeatedly in a day or on consecutive days. Also, wash treated clothing before wearing it again. (This precaution may vary with different repellents—check the product label.)

• If you or your child get a rash or other bad reaction from an insect repellent, stop using the repellent, wash the repellent off with mild soap and water, and call a local poison control center for further guidance. If you go to a doctor because of the repellent, take the repellent with you to show the doctor.

Note that the label for products containing oil of lemon eucalyptus specifies that they should not to be used on children under the age of three years. Other than those listed above, EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women, or on children. For additional information regarding the use of repellent on children, please see CDC’s Frequently Asked Questions about Repellent Use. [http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm]

DEET-based repellents applied according to label instructions may be used along with a separate sunscreen. No data are available at this time regarding the use of other active repellent ingredients in combination with a sunscreen.




Vertebrate Ecology Transmission Cycle

West Nile (WN) virus is amplified during periods of adult mosquito blood-feeding by continuous transmission between mosquito vectors and bird reservoir hosts. Infectious mosquitoes carry virus particles in their salivary glands and infect susceptible bird species during blood-meal feeding. Competent bird reservoirs will sustain an infectious viremia (virus circulating in the bloodstream) for 1 to 4 days after exposure, after which these hosts develop life-long immunity. A sufficient number of vectors must feed on an infectious host to ensure that some survive long enough to feed again on a susceptible reservoir host.

View enlarged image.

People, horses, and most other mammals are not known to develop infectious-level viremias very often, and thus are probably "dead-end" or incidental-hosts.

Birds

West Nile virus has been detected in dead birds of at least 138 species. Although birds, particularly crows and jays, infected with WN virus can die or become ill, most infected birds do survive. Click here for more information on species of dead birds in the U.S. in which West Nile virus has been detected.

There is no evidence that a person can get WN virus from handling live or dead infected birds. Persons should avoid bare-handed contact when handling any dead animals, and use gloves or double plastic bags to place the bird carcass in a garbage bag or contact their local health department for guidance.

Dogs and Cats

West Nile virus does not appear to cause extensive illness in dogs or cats. There is a single published report of WN virus isolated from a dog in southern Africa (Botswana) in 1982. West Nile virus was isolated from a single dead cat in 1999. A serosurvey in New York City of dogs in the 1999 epidemic area indicated that dogs are frequently infected. Nonetheless, disease from WN virus infection in dogs has yet to be documented.

There is no documented evidence of person-to-person or animal-to-person transmission of WN virus. Because WN virus is transmitted by infectious mosquitoes, dogs or cats could be exposed to the virus in the same way humans become infected. Veterinarians should take normal infection control precautions when caring for an animal suspected to have this or any viral infection. It is possible that dogs and cats could become infected by eating dead infected animals such as birds, but this is undocumented.


http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm




There is no reason to destroy an animal just because it has been infected with WN virus. Full recovery from the infection is likely. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Horses

Cases of WN virus disease in horses have been documented, either by virus isolation or by detection of WN virus-neutralizing antibodies in 1999, 2000, and 2001. Approximately 40% of equine WN virus cases results in the death of the horse. Horses most likely become infected with WN virus in the same way humans become infected, by the bite of infectious mosquitoes.

In locations where WN virus is circulating, horses should be protected from mosquito bites as much as possible. Horses vaccinated against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE) are NOT protected against WN virus infection. A West Nile virus vaccine for horses was recently licensed, but its effectiveness is unknown. Horses infected by WN virus develop a brief low-level viremia that is rarely, if ever, infectious to mosquitoes. There is no reason to destroy a horse just because it has been infected with WN virus. Data suggest that most horses recover from the infection. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Other Vertebrates

Through December 2001, CDC has also received a small number of reports of WN virus infection in bats, a chipmunk, a skunk, a squirrel, and a domestic rabbit.

Entomology Arthropod-borne viruses (termed "arboviruses") are viruses that are maintained in nature through biological transmission between susceptible vertebrate hosts by blood-feeding arthropods (mosquitoes, sand flies, ceratopogonids "no-see-ums", and ticks). Vertebrates can become infected when an infected arthropod bites them to take a blood meal. The term 'arbovirus' has no taxonomic significance.

The arboviral encephalitides are zoonotic, being maintained in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector. These cycles usually remain undetected until humans encroach on a natural focus, or the virus escapes this focus via a secondary vector or vertebrate host as the result of some ecologic change. Humans and domestic animals can develop clinical illness but usually are incidental or "dead-end" hosts because they do not produce significant viremia (circulating virus), and thus do not contribute to the transmission cycle.



In the United States, West Nile virus is transmitted by infected mosquitoes, primarily members of the Culex species.

Arboviral encephalitis can be prevented in two major ways:


1. Personal protective measures to reduce contact with mosquitoes and

2. Public health measures to reduce the population of infected mosquitoes in the environment.

Personal protection measures include reducing time outdoors, particularly in early morning and evening hours, wearing long pants and long sleeved shirts, and applying mosquito repellent to exposed skin areas and clothing.

Image: Culex mosquito laying eggs. (View enlarged image.)

Public health measures include elimination of larval habitats or spraying of insecticides to kill juvenile (larvae) and adult mosquitoes. The combination of mosquito control methods selected for use in a control program depends on the time of year, the type of mosquitoes to be controlled, and the habitat structure. In emergency situations, wide area aerial spraying is used to quickly reduce the number of adult mosquitoes. In many states, aerial spraying may be available as a means to control nuisance mosquitoes. Such resources can be redirected to areas of virus activity when necessary.

Financing of aerial spraying costs during disease outbreaks is often provided by state or local emergency funds. Federal funding of emergency spraying is rare and almost always is associated with a natural disaster such as flood or hurricane.

Virology: Classification of West Nile Virus

1. Family: Flaviviridae 2. Genus: Flavivirus Japanese Encephalitis Antigenic Complex 3. Complex includes: Alfuy, Cacipacore, Japanese encephalitis, Koutango,

Kunjin, Murray Valley encephalitis, St. Louis encephalitis, Rocio, Stratford, Usutu, West Nile, and Yaounde viruses.

4. Flaviviruses: share a common size (40-60nm), symmetry (enveloped, icosahedral nucleocapsid), nucleic acid (positive-sense, single stranded RNA approximately 10,000-11,000 bases), and appearance in the electron


http://www.cdc.gov/ncidod/dvbid/westnile/mosquitoSpecies.htm

http://www.cdc.gov/ncidod/dvbid/westnile/culex-image.htm


microscope. Therefore, images of West Nile virus are representative for this group of viruses.

Public Health Confronts the Mosquito: Developing Sustainable State and Local Mosquito Control Programs

Report by Association of State and Territorial Health Officials

See "What You Can Do About Mosquito Control"

Report Overview State and Local Mosquito Control Mosquito control is an important and basic public health function. The rapid spread of West Nile virus across the U.S. in the last five years demonstrates the continuing need for organized mosquito control activities. States and local communities are challenged to develop and maintain these essential vector control programs, especially in tight budgetary times and when emergency situations have quieted.

The Association of State and Territorial Health Officials’ Mosquito Control Collaborative, a body comprised of state, local, and federal representatives from public health, environmental, and agricultural agencies, as well as other organizations closely involved with vector control and public health, has developed a report titled Public Health Confronts the Mosquito Control: Developing Sustainable State and Local Mosquito Control Programs. The report contains four sections discussing the major components of successful state and local mosquito control efforts:

• Planning Ahead Understanding the structures and roles of the state, local and federal participants, defining workforce and training requirements, identifying legal authorities and funding alternatives, and developing strategies for evaluating programs are elements that should be included in any successful planning effort. States, localities, and the federal government all have active roles in mosquito control. The exact roles of each will differ among the individual states and localities. Whatever structure is chosen, it should be based on solid legal authority to act. The structure of the funding mechanism for mosquito control activities also impacts the ultimate sustainability of the program or activities.

• Involving Others The foundation to any successful mosquito control action is involving key participants early in the process. Governments should develop a strategy for involving others, which includes identifying and engaging a wide variety of stakeholders. Governments



should take care to identify the individuals, organizations, and agencies with a stake in mosquito control decisions. A variety of mechanisms should be used to target appropriate outreach to stakeholders. Special care should also be given to provide decision makers with solid information upon which to base policy.

• Use the Best Science and Data It is critical that science drives the assessment of local and state needs, strategies selected, and design and monitoring of mosquito control programs. There are numerous proven methodologies and practices that guide the best mosquito control programs. All programs need to be based on an identified need that is matched with local and state resources and technically sound strategies. Access to epidemiologic capacity to conduct surveillance of mosquito-borne diseases in the human population, and monitor disease and the distribution of relevant animal and insect populations, is critical to begin any mosquito control activity. States and localities must also determine their mosquito control needs. A scientific response to combat nuisance mosquitoes may look very different from a program to combat mosquitoes carrying disease.

• Informing the Public Mosquito control programs need the support of an informed public. Many of the successful strategies for control involve individuals, their families, and their neighborhoods. The public also has concerns about the problems related to mosquito populations and about insecticides and spraying. Development of a communications plan that includes public education about preventing the breeding of mosquitoes, personal protection guidance, and the activities and success of the agencies involved is critical to the success of the program.

Conclusion Mosquito control is a multi-discipline effort that can and should involve many agencies and organizations at the local, state, and federal level. When programs are started for a specific disease threat, there is often a temptation to abandon control efforts once the threat has passed. As history demonstrates, the mighty mosquito always returns and frequently with a previously unknown and unpredictable disease threat. Public health has a responsibility and an opportunity to be part of a comprehensive and thoughtful approach to continued mosquito control through partnerships and teamwork at all levels of government. More information about state and local mosquito control programs and a copy of Public Health Confronts the Mosquito is available at www.astho.org/?template=mosquito_control.html. The report also contains Planning and Action checklists highlighting the major decision points and recommendations.

Source: Public Health Confronts the Mosquito: Developing Sustainable State and Local Mosquito Control Programs. Association of State and Territorial Health Officials. (June 2005). Available at www.astho.org/?template=mosquito_control.html.

What You Can Do About Mosquito Control

• Find out about your local mosquito control program

Contact them for information or questions about their mosquito control practices. West Nile Virus Guide


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.astho.org/?template=mosquito_control.html



• Support mosquito control activities

Report mosquito breeding sites untended pools, discarded tires, drainage ditches with standing water.

• If your community doesn't have a mosquito control program

Contact your local government officials (blue pages of the phone book) or health department. Information in the Public Health Confront the Mosquito (described above) provides guidance about starting a program.






Mosquitoes Each summer, hordes of these insects descend on backyards, parks and campgrounds. While most mosquitoes are merely nuisances, some can transmit serious diseases such as encephalitis and malaria in humans and heartworm disease in dogs.

While the principles for west nile virus and mosquitoes are fairly common from state to state and generally worldwide, it would be impossible to discuss the specifics for all areas of the globe in a short volume such as this. So when possible I’ll relate to the west nile virus and mosquito control with regard to the state I live in, Illinois. Keep in mind this in no way denigrates the material in this book. All mosquitoes lay eggs in water, the virus is transferred via birds. Most specifics come from the Center for Disease Control and State Health Departments.

What kinds of mosquitoes are common in Illinois?

Two different kinds of mosquitoes plague Illinoisans. Floodwater (temporary pool) mosquitoes deposit their eggs singly in low-lying areas that will be flooded later. Under normal summer temperatures, large numbers of biting mosquitoes will emerge about two weeks after heavy rains and can be a major nuisance problem for several

weeks. The most common of these in Illinois is the inland floodwater mosquito. A vicious biter, this mosquito will commonly fly 10 or more miles from where they hatch, particularly along prevailing winds. Floodwater mosquitoes have not been significant disease carriers in Illinois.

Vector mosquitoes carry diseases and lay their eggs in stagnant ditches and sewage treatment ponds or water in treeholes, old tires, clogged gutters, old tin cans and anything else that will hold water. Eggs are laid on or just above the water surface, where they usually hatch within two to three days. Two of the more common vector mosquitoes in Illinois are the Culex, or house mosquito, and the tree-hole mosquito. Neither migrates long distances.

Another disease-carrying mosquito is the Asian tiger mosquito, which arrived in the United States in 1985 in old tires. An aggressive day-biting mosquito, it breeds in large numbers in water-filled artificial containers.

Do all mosquitoes carry disease?

Floodwater mosquitoes are not major vectors of human disease in Illinois, but they do transmit heartworm disease in dogs, as do Culex mosquitoes. The worms live and reproduce in the heart and pulmonary vessels and can severely weaken or kill the dog.



Although difficult to treat, the disease is easily prevented by medication prescribed by a veterinarian.

In Illinois, the most common human illness carried by mosquitoes is encephalitis. This inflammation of the brain is caused by viruses and the disease can range from mild to severe. Severe symptoms include rapid onset of severe headaches, high fever and mental disturbances, such as confusion, irritability, tremors, stupor and coma. Severe cases sometimes end in death or with survivors suffering permanent physical and mental disabilities.

Mosquitoes do not carry all types of encephalitis virus, but they do carry at least three that can cause illness. The Culex mosquito, which bites from dusk to dawn, is a vector of St. Louis encephalitis and West Nile virus; it becomes infected by feeding on birds that carry these viruses. St. Louis encephalitis and West Nile virus affect mainly older adults. The tree-hole mosquito, which bites during the day, is the main vector of California (LaCrosse) encephalitis in Illinois. The virus infects chipmunks, squirrels and other small woodland animals; in humans, it affects mainly children. The Asian tiger mosquito transmits dengue fever in other parts of the world and could become involved in the California encephalitis cycle in Illinois.

The last major nationwide epidemic of mosquito-borne encephalitis occurred in 1975. In Illinois, 578 cases of St. Louis encephalitis, which resulted in 47 deaths, and 23 cases of California encephalitis were identified during that year.

When was West Nile virus found in Illinois?

West Nile virus was first identified in September 2001 when laboratory tests confirmed its presence in two dead crows found in the Chicago area. The following year, the state's first human cases and deaths from West Nile disease were recorded and all but two of the state's 102 counties eventually reported a West Nile positive, human, bird, mosquito or horse. By the end of 2002, Illinois had counted more human cases (884) and deaths (66) than any other state in the nation. In 2003, the number of human cases fell to 54 and only one death, and West Nile activity was reported in 77 counties.

What is the best way to reduce populations of mosquitoes?

The first and best defense against these pests and the illnesses they may carry ito eliminate the places where they breed. Here are a few suggestions:

s

• Remove or empty water in old tires, tin cans, buckets, drums, bottles or other places where mosquitoes might breed. Be sure to check clogged gutters and flat roofs that may have poor drainage. Make sure cisterns, cesspools, septic tanks, fire barrels, rain barrels and trash containers are covered tightly with a lid or with 16-mesh screen.



• Empty plastic wading pools at least once a week and store indoors when not in use. Unused swimming pools should be covered or drained during the mosquito season. (Note: If you choose to drain your pool, be sure the hydrostatic relief valve is open in order to keep it from floating out of the ground if the water table rises.)

• Change the water in bird baths and plant pots or drip trays at least once each week.

• Store boats covered or upside down, or remove rainwater weekly. • Empty your pet's water bowl daily. • Level the ground around your home so water can run off and not collect in low

spots. Fill in holes or depressions near your home that accumulate water. • Fill in tree rot holes and hollow stumps that hold water. • If you have an ornamental water garden, stock it with mosquito-eating fish (e.g.,

minnows, "mosquito fish," or goldfish). They eat mosquito larvae. • Keep weeds and tall grass cut short; adult mosquitoes look for these shady places

to rest during the hot daylight hours. • Use a flyswatter or household spray to kill mosquitoes, flies or other insects that

get into buildings. Spray shrubbery and high weeds to kill adult insects. (Check the insecticide label to make the sure the spray will not damage flowers or ornamental plants.)

• Small impoundments of water can be treated for mosquito larvae with "Bti," a bacterial insecticide. Many hardware stores carry doughnut-shaped Bti briquets (Mosquito Dunks R) for this purpose. Be sure to follow the insecticide label directions exactly.

• Some mosquito control methods are not very effective. Bug zappers are not effective in controlling biting mosquitoes. Various birds and bats will eat mosquitoes, but there is little scientific evidence that this reduces mosquitoes around homes.

• Community-wide mosquito abatement efforts can be quite effective if they are conducted as part of an integrated pest management program. This includes monitoring and draining or treating areas where mosquitoes breed — such as street catch basins, occasionally flooded marshes, river backwater areas, swamps and other low-lying areas.

How can people protect themselves from mosquito bites?

• Avoid places and times when mosquitoes bite. Generally, the peak biting periods occur just before and after sunset and again just before dawn. Each species, however, has its own peak period of biting. Tree-hole and Asian tiger mosquitoes, for example, feed during daylight hours in or near shaded or wooded areas.

• Be sure door and window screens are tight-fitting and in good repair. • Wear appropriate clothing. Long-sleeved tops and long pants made of tightly

woven materials keep mosquitoes away from the skin. Be sure, too, that your clothing is light colored. Keep trouser legs tucked into boots or socks.

• Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect small babies any time.

• When it is necessary to be outdoors, apply insect repellent as indicated on the repellent label. The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate. Apply repellents to clothes whenever possible; apply sparingly



to exposed skin if label permits. Consult a physician before using repellents on young children.

Mosquitoes and Encephalitis

The Problem - Mosquito bites cause itching and irritation, and scratching may result in infected sores. Mosquitoes also transmit serious and sometimes fatal diseases to humans and their pets.

Diseases - Encephalitis is an inflammation of the brain that can be caused by viruses. The symptoms of encephalitis can range from mild to severe. Severe symptoms include rapid onset of severe headaches, high fever, and mental disturbances such as confusion, irritability, tremors, stupor and coma. Severe cases sometimes end in death or with survivors suffering permanent loss of limb function, reduction of intelligence and/or emotional instability.

Not all types of encephalitis viruses are carried by mosquitoes. However, mosquitoes carry at least two types of encephalitis viruses that cause human disease in Illinois. La Crosse (California) encephalitis is normally an infection of squirrels and chipmunks; in humans it affects mainly children. St. Louis encephalitis is an infection of wild birds; in humans it affects mainly older adults.

Mosquitoes can also infect dogs with heartworm. The worms live in the heart and can severely weaken or kill the dog. Although difficult to treat, this disease is easily prevented by medication that can be prescribed by your veterinarian.

Prevent Mosquitoes from Breeding Around the Home Mosquito larvae or "wrigglers" must live in still water for five or more days to complete their growth before changing into adult biting mosquitoes capable of transmitting disease. Often, the number of mosquitoes in an area can be reduced by removing sources of standing water. Hundreds of mosquitoes can come from a single discarded tire.

• Get rid of old tires, tin cans, buckets, drums, bottles oany water-holding containers.

r

• Fill in or drain any low places (puddles, ruts, etc.) in the yard.

• Keep drains, ditches, and culverts free of weeds and trash so water will drain properly.

• Keep roof gutters free of leaves and other debris. • Cover trash containers to keep out rainwater.



• Repair leaky pipes and outside faucets. • Empty plastic wading pools at least once a week and store indoors when not in use.

Unused swimming pools should be drained and kept dry during the mosquito season.

• Fill in tree rot holes and hollow stumps that hold water. • Change the water in bird baths and plant pots or drip trays at least once each week. • Store boats covered or upside down, or remove rainwater weekly. • Keep grass cut short and shrubbery well trimmed around the house so adult

mosquitoes will not hide there.

Only a constant, complete program to control mosquitoes will reduce the numbers, the nuisance and the danger of disease.

Protection from Mosquito Bites Although many kinds of mosquitoes bite at dusk or at night, some kinds will bite during the day. Almost all kinds will try to bite if you enter an area where they are resting, like high grass.

• When possible, avoid places and times when mosquitoes bite. • Wear light-colored protective clothing: Tightly woven materials that cover arms and

legs provide some protection from mosquito bites. Keep trouser legs tucked into boots or socks, and collars buttoned.

• Have good screening: Make sure door and window screens fit tightly and all holes are repaired.

• Use mosquito netting when sleeping outdoors or in an unscreened structure, and to protect small babies any time.

• Small impoundments of water can be treated for mosquito larvae with "Bti," a bacterial insecticide. Many hardware stores carry doughnut-shaped Bti briquets (Mosquito Dunks R) for this purpose. Be sure to follow the insecticide label directions exactly.

• When participating in outdoor activities where mosquitoes are biting, wear protective clothing (shoes, socks, shirt and long pants). For additional protection from mosquitoes, use an insect repellent. The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate. Apply repellents to clothes whenever possible; apply sparingly to exposed skin if label permits. Consult a physician before using repellents on young children.

• Spraying your backyard with an insecticidal fog or mist is effective only for a short time. Mosquitoes will return when the effect of the spray has ended.

• Insect light electrocutors ("bug zappers") or sound devices do little to reduce biting mosquitoes in an area.

• Installing bird or bat houses to attract these insect-eating animals has been suggested as a method of mosquito control. However, there is little scientific evidence that this significantly reduces the mosquito population around homes.

• Some communities conduct community-wide mosquito abatement programs. Whenever possible, the primary effort of such programs should be identification of mosquito-breeding sites, followed by removal or treatment of these sites with an insecticide used for control of mosquito larvae.



Questions and Answers about Mosquito Prevention for People, Property and Pets

What kinds of diseases can be carried by mosquitoes?

Mosquito-borne disease is rare in Illinois. However, mosquitoes can carry at least three encephalitis viruses that cause human disease.

La Crosse (California) encephalitis is normally an infection of squirrels and chipmunks; in humans it affects mainly children. St. Louis encephalitis is an infection of wild birds; in humans it affects mainly older adults. In 2001, West Nile virus (WNV) was detected for the first time in Illinois in birds, horses and mosquitoes. West Nile virus, like St. Louis encephalitis, causes encephalitis primarily in older adults.

What is encephalitis?

Encephalitis is an inflammation of the brain that can be caused by arboviruses (viruses carried by arthropods, such as mosquitoes and ticks) or by other types of viruses. In Illinois, arboviruses are primarily transmitted to humans by the bites of infected mosquitoes. Most individuals who are bitten by an infected mosquito will experience no symptoms of the disease or will have only very mild symptoms. Approximately 1 percent to 2 percent will develop recognizable symptoms. Some persons may have mild symptoms, such as a fever and headache. Severe infection may cause rapid onset of severe headache, high fever, muscle aches, stiffness in the back of the neck, problems with muscle coordination, disorientation, convulsions and coma. Symptoms usually occur five to 15 days after the bite of an infected mosquito. Not all viruses that cause encephalitis are carried by mosquitoes.

How can I help protect my family and myself from mosquitoes and the diseases they may carry?

During the summer, mosquitoes can develop in any standing water that lasts more than seven to 10 days. Consequently, you can begin protecting your family from mosquitoes by reducing the amount of standing water available for mosquito breeding around your home:

• Dispose of discarded tires, cans, plastic containers, ceramic pots or other unused similar water-holding containers that have accumulated on your property. Do not



overlook containers that have become overgrown by vegetation.

• At least once per week, empty standing water from containers on your property, such as tire swings, or bird baths.

• Fill in tree rot holes and hollow stumps that hold water.

• Drill holes in the bottom of recycling containers that are left outdoors. Drainage holes drilled in the sides of containers allow sufficient water to collect in which mosquitoes may breed.

• Clean clogged roof gutters, particularly if the leaves from surrounding trees have a tendency to plug up the drains. Flooded roof gutters are easily overlooked but can produce hundreds of mosquitoes each season.

• Turn over plastic wading pools when not in use. A wading pool becomes a mosquito producer if it is not used on a regular basis.

• Turn over wheelbarrows and do not allow water to stagnate in bird baths. Change water in bird baths and wading pools on a weekly basis.

• Store boats covered or upside down, or remove rainwater weekly. • Aerate ornamental pools or stock them with fish. Water gardens are fashionable but

become major mosquito producers if they are allowed to stagnate. • Clean and chlorinate swimming pools that are not being used. A swimming pool that

is left untended by a family that goes on vacation for a month can produce enough mosquitoes to result in neighborhood-wide complaints. Be aware that mosquitoes may breed in the water that collects on swimming pool covers.

• Keep drains, ditches and culverts free of grass clippings, weeds and trash so water will drain properly.

• Fill in low areas on your property to eliminate standing water. Ponds or streams where fish are present or the water is disturbed by current or wave action do not produce many mosquitoes.

• Report possible mosquito breeding sites to your local mosquito control agency if one exists in your community.

Should we stay indoors?

It is not necessary to limit outdoor activities unless there is evidence of mosquito-borne disease in your area. However, you can and should try to reduce the risk of being bitten by mosquitoes.

• Minimize time spent outdoors between dusk and dawn when mosquitoes are most active.

Northern house mosquito (Culex pipiens) 1



• Be sure door and window screens are tight-fitting and in good repair. • Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long

periods of time, or when mosquitoes are most active. Clothing should be light colored and made of tightly woven materials to keep mosquitoes away from the skin.

• Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect small babies when outdoors.

• When it is necessary to be outdoors, apply insect repellent as indicated on the repellent label. The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate. Apply repellents to clothes whenever possible; apply sparingly to exposed skin if label permits. Consult a physician before using repellents on young children.

• Insect light electrocutors ("bug zappers") or sound devices do little to reduce biting mosquitoes in an area.

• Spraying your backyard with an insecticidal fog or mist is effective only for a short time. Mosquitoes will return when the effect of the spray has ended.

• Installing bird or bat houses to attract these insect-eating animals has been suggested as a method of mosquito control. However, there is little scientific evidence that this significantly reduces the mosquito population around homes.

Can pets and livestock get WNV infection?

Horses can become infected with WNV if bitten by mosquitoes that carry the virus. There is a published report of West Nile virus isolated from a dog in southern Africa (Botswana) in 1982. West Nile virus has been isolated from several dead cats in 1999 and 2000. A blood of dogs and cats in the epidemic area showed a low infection rate.

What signs of infection should I look for in domestic animals?

West Nile virus and other mosquito-borne viruses can cause encephalitis in domestic animals. Sick animals may have a fever, weakness, poor muscle coordination, muscle spasms and signs of a neurological disease, such as change in temperament or seizures.

What should I do if I suspect my pet has WNV?

If your animal is sick, contact your veterinarian. The veterinarian will evaluate your animal, provide treatment and forward samples for laboratory testing to rule out other possible diseases. The Illinois Department of Agriculture can help veterinarians determine if WNV is the cause once the illness is reported.

Can you get WNV directly from birds, game or domestic animals?

The risk to humans and domestic animals is from the bite of WNV-infected mosquitoes. Although there is no evidence of human infection from handling infected live or dead animals, the U.S. Centers for Disease Control and Prevention recommends that anyone handling sick or dead animals avoid bare-handed contact. Hunters should use gloves when cleaning game animals and persons disposing of dead birds should use a shovel, gloves or



double plastic bags to place carcasses in a garbage can. After disposing of the carcass, thoroughly wash your hands with soap and warm water. Veterinarians should use normal veterinary infection control precautions when caring for a horse suspected to have this or any other infection.

Is there a vaccine for pets and livestock for WNV?

A vaccine is available to protect horses from WNV infection; vaccines for other domestic animals are not available currently.

How is WNV infection in domestic animals treated?

As in people, there are no specific treatments for WNV infection in domestic animals. Treatment is primarily supportive to lessen the severity of the symptoms.

How can I protect pets and livestock from WNV infection?

You can reduce the risk of WNV infection in animals by minimizing their exposure to infected mosquitoes.

Questions and Answers about Spraying for Adult Mosquitoes

How are adult mosquitoes controlled?

Mosquito control agencies use truck-mounted fogging units to apply insecticides as an ultra-low-volume (ULV) spray. ULV spray units dispense very fine aerosol droplets (fog) that stay aloft and kill mosquitoes on contact. The amount of insecticide sprayed by ULV units is small compared to the area treated, usually about 3 to 5 ounces per acre, which minimizes exposure and risks to people and the environment. Some communities have thermal foggers that use an oil carrier that is heated to disperse the pesticide in a dense smoke-like fog.

What agency conducts mosquito control in my town?

With a few exceptions, where mosquito control is conducted, it is locally funded and carried out by village or city governments. Some communities are part of a local government agency called a mosquito abatement district that receives local property taxes to conduct mosquito controperations.

ol

Why is the local government fogging for mosquitoes in my community?



Some communities decide to fog because of the nuisance caused by hoards of biting mosquitoes. In some situations, officials may decide to fog because testing of mosquitoes and wild birds may have shown that mosquito-borne West Nile virus or St. Louis encephalitis virus is present in the community. Contact your local government or mosquito control agency to determine why that agency has decided to fog for mosquitoes.

Why do they fog for mosquitoes when I am out taking my evening walk?

The best time to kill adult mosquitoes by fogging is at dusk, when they are most active and looking for food (mosquitoes feed on human or animal blood). The aerosol fog primarily targets flying mosquitoes, which is why the timing of the spray is critical.

Will local officials notify me before fogging?

Most states have no law that requires local governments to notify citizens before fogging for mosquitoes. However, many mosquito control agencies will notify individuals who request notification before fogging begins. Contact your local government office or mosquito control agency if you wish to be notified.

What insecticides are used to fog for mosquitoes?

The most commonly used products are synthetic pyrethroid insecticides (such as Scourge ®and Anvil ®), pyrethrins and malathion. All insecticides used for mosquito control in most states must be registered with the U.S. Environmental Protection Agency (USEPA) and the Illinois Department of Agriculture (IDA). You can find fact sheets about some insecticides commonly used to kill mosquitoes on the USEPA web site, http://www.epa.gov/opp00001/factsheets/skeeters.htm

How long does the fog kill mosquitoes?

During the fogging, flying mosquitoes within the treated area are killed. Although the local mosquito population is reduced for a few days, fogging does not prevent mosquitoes from re-entering the area.

If the city has been fogged for mosquitoes, are all mosquitoes in my area eliminated?

Fogging will kill only part of the mosquitoes in your area for a few days. Consequently, individuals should always use personal protection when mosquitoes are present:

• When possible, avoid places and times when mosquitoes bite. • Wear light-colored protective clothing. Tightly woven materials that cover arms and

legs provide some protection from mosquito bites. Keep trouser legs tucked into boots or socks, and collars buttoned.

• Make sure door and window screens fit tightly and all holes are repaired. • Use mosquito netting when sleeping outdoors or in an unscreened structure, and to

protect small babies any time they are outside. • If participating in outdoor activities when mosquitoes are biting, wear protective

clothing (shoes, socks, shirt and long pants). For additional protection from


http://www.epa.gov/opp00001/factsheets/skeeters.htm


mosquitoes, use an insect repellent. The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate. Apply repellents to clothes whenever possible; apply sparingly to exposed skin if label permits. Consult a physician before using repellents on young children.

Are the insecticides used for fogging safe?

The USEPA reviews and approves insecticides (and other pesticides) and their labeling to ensure those used to protect public health are applied by methods that minimize the risk of human exposure and adverse health and environmental effects. Generally, there is no need to relocate during mosquito control fogging. The insecticides have been evaluated for this use and have been found to pose minimal risk to human health and the environment when used according to label directions. For example, USEPA has estimated the exposure and risks to both adults and children posed by ULV aerial and ground applications of the insecticides malathion and naled. For all the scenarios considered, exposures ranged from 100 to 10,000 times below the amount of pesticide that might pose a health concern. These estimates assumed several spraying events over a period of weeks and also assumed that a toddler would ingest some soil and grass in addition to dermal exposure. Other mosquito control insecticides pose similarly low risks. Nevertheless, because insecticides are inherently toxic, no pesticide is absolutely risk free. The likelihood of experiencing adverse health effects as a result of exposure to any pesticide depends primarily on the amount of pesticide that a person contacts and the amount of time the person is in contact with that pesticide. In addition, a person's age, sex, genetic makeup, lifestyle and/or general health characteristics can affect his or her likelihood of experiencing adverse health effects as a result of exposure to insecticides. Although mosquito control insecticides pose low risks, some people may prefer to minimize or to avoid exposure to these chemicals. Here are some common sense steps to help reduce possible exposure to insecticides:

• Listen and watch for announcements in the local media about fogging for mosquitoes and remain indoors during the application in your neighborhood.

• If possible, remain inside whenever fogging takes place. • People who suffer from chemical sensitivities or feel fogging could aggravate a

preexisting health condition should consult their doctor or local health department and take special measures to avoid exposure.

• Close windows and doors and turn off your air conditioning (or set it to circulate indoor air) when fogging is taking place in the immediate area.

• Do not let children play near or behind truck-mounted applicators when they are in use. To ensure the fogging trucks have left the area, keep children inside during fogging and for about one hour after fogging.

• Bring pets inside and cover ornamental fish ponds to avoid direct exposure. • Consult your doctor if you think you are experiencing health effects from the

fogging. • More information about spraying for adult mosquitoes may be found on the

USEPA's Web site: <http://www.epa.gov/pesticides/citizens/pmcfs.pdf>.

Do I need to wash home-grown fruits and vegetables after the mosquito fogging?



The amount of insecticide used to fog for adult mosquitoes is much smaller than that used to spray fruit and vegetable insect pests. However, it is always a good idea to wash fruits and vegetables before eating them to remove soil and other contaminants.

What should I do if I have medical questions about insecticides?

• If you suspect that you are reacting to an insecticide, call your physician or local poison control center. The Illinois Poison Center emergency telephone number is 1-800-222-1222; 312-906-6185 (TTY/TDD).

• Additional information about the active ingredients in insecticides may be obtained from the National Pesticide Information Center (NPIC) at 1-800-858-7378 from 8:30 a.m. to 6:30 p.m. (Central time) seven days a week, excluding holidays; or visit NPIC's Web site at <http://npic.orst.edu/>.

Will the fogging kill birds or other large animals?

During the pesticide registration process, USEPA considers the effect of insecticides on wildlife. If the insecticide is applied according to label directions, wildlife should not be killed or injured with the exception of insects similar in size to mosquitoes. If you have any concerns about this issue after they have sprayed in your area, contact IDA.

Are individuals who do mosquito control required to be licensed?

Yes, all individuals who use insecticides to control mosquitoes are required to be licensed by IDA. There are two exceptions: homeowners who fog for mosquitoes on their own residential property and individuals who use certain insecticides to treat tires for mosquitoes at tire shops, tire recycling sites and similar businesses. For information about mosquito control licensing, call IDA at 217-785-2427.

Can I fog my backyard for mosquitoes?

If you choose to fog your yard for mosquitoes, be sure to use only insecticides labeled for control of adult mosquitoes. Be sure to follow the label directions exactly. However, spraying your backyard with an insecticidal fog or mist is effective only for a short time. If the insecticide label permits, spraying dense vegetation like that found along the edge of a woods where mosquitoes rest will last somewhat longer. Mosquitoes will return when the effect of the spray has ended.

Can I treat a depression that floods in my backyard for mosquitoes?

If the depression floods for 10 or more days, it can produce mosquitoes. However, use ONLY insecticides that are labeled for treating water for mosquitoes. Small impoundments of water can be treated for mosquito larvae with "Bti," a bacterial insecticide. One product that is available at many hardware stores for this purpose is doughnut-shaped Bti briquets (Mosquito Dunks ®). Be sure to follow the insecticide label directions exactly.

Can communities use other methods to control mosquitoes besides fogging?



Yes, some communities conduct community-wide mosquito abatement programs. Whenever possible, the primary effort of such programs should be identification of mosquito-breeding sites, followed by removal or treatment of these sites with an insecticide used for control of mosquito larvae (the immature form of a mosquito). Also, homeowners should remove old tires and other unused water-holding containers, change the water in birdbaths, and drain wading pools weekly. Insect light electrocutors ("bug zappers") or sound devices do little to reduce biting mosquitoes in an area. Installing bird or bat houses to attract these insect-eating animals has been suggested as a method of mosquito control. However, there is little scientific evidence that this significantly reduces the mosquito population around homes.

The EPA, Pesticides and Mosquito Control

Mosquito-borne diseases affect millions of people worldwide each year. In the United States, some species of mosquitoes can transmit diseases such as encephalitis, dengue fever, and malaria to humans, and a variety of diseases to wildlife and domestic animals. To combat mosquitoes and the public health hazards they present, many states and localities have established mosquito control programs. These programs, which are based on surveillance, can include nonchemical forms of prevention and control as well as ground and aerial application of chemical and biological pesticides.

The mission of the Environmental Protection Agency (EPA) is to protect human health and the environment. EPA reviews and approves pesticides and their labeling to ensure that the pesticides used to protect public health are applied by methods that minimize the risk of human exposure and adverse health and environmental effects. In relation to mosquito control, the Agency also serves as a source of information about pesticide and nonpesticide controls to address the concerns of the general public, news media, and the state and local agencies dealing with outbreaks of infectious diseases or heavy infestations of mosquitoes. The following questions and answers provide some basic information on mosquito control, safety precautions, and information on insecticides used for mosquito control programs.

How Does EPA Ensure the Safest Possible Use of Pesticides?

EPA must evaluate and register pesticides before they may be sold, distributed, or used in the United States. The Agency is also in the process of reassessing, and reregistering when appropriate, all older pesticides (those registered prior to 1984) to ensure that they meet current scientific standards. To evaluate a pesticide for either registration or re-registration, EPA assesses a wide variety of potential human health and environmental effects associated with use of the product. The producer of the pesticide must provide data from tests done according to EPA guidelines. These tests determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish, and plants, including endangered species and nontarget organisms. Other tests help to assess the risks of contaminating surface water or ground water from leaching, runoff, or spray drift. If a pesticide meets EPA requirements, the pesticide is approved for use in accordance with



label directions. However, no pesticide is 100 percent safe and care must be exercised in the use of any pesticide.

How Are Mosquitoes Controlled with Pesticides and Other Methods?

The first step in mosquito control is surveillance. Mosquito specialists conduct surveillance for diseases harbored by domestic and nonnative birds, including sentinel chickens (used as virus transmission indicators), and mosquitoes. Surveillance for larval habitats is conducted by using maps and aerial photographs, and by evaluating larval populations. Other techniques include various light traps, biting counts, and analysis of reports from the public. Mosquito control programs also put high priority on trying to prevent a large population of adult mosquitoes from developing so that additional controls may not be necessary. Since mosquitoes must have water to breed, methods of prevention may include controlling water levels in lakes, marshes, ditches, or other mosquito breeding sites, eliminating small breeding sites if possible, and stocking bodies of water with fish species that feed on larvae. Both chemical and biological measures may be employed to kill immature mosquitoes during larval stages. Larvicides target larvae in the breeding habitat before they can mature into adult mosquitoes and disperse. Larvicides include the bacterial insecticides Bacillus thuringiensis israelensis and Bacillus sphaericus, the insect growth inhibitor methoprene, and the organophosphate insecticide temephos. Mineral oils and other materials form a thin film on the surface of the water which cause larvae and pupae to drown. Liquid larvicide products are applied directly to water using backpack sprayers and truck or aircraft-mounted sprayers. Tablet, pellet, granular, and briquet formulations of larvicides are also applied by mosquito controllers to breeding areas.

Adult mosquito control may be undertaken to combat an outbreak of mosquito-borne disease or a very heavy nuisance infestation of mosquitoes in a community. Pesticides registered for this use are adulticides and are applied either by aircraft or on the ground employing truck-mounted sprayers. State and local agencies commonly use the organophosphate insecticides malathion and naled and the synthetic pyrethroid insecticides permethrin, resmethrin, and sumithrin for adult mosquito control.

Mosquito adulticides are applied as ultra-low volume (ULV) sprays. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill flying mosquitoes on contact. ULV applications involve small quantities of pesticide active ingredient in relation to the size of the area treated, typically less than 3 ounces per acre, which minimizes exposure and risks to people and the environment.

What Can I Do to Reduce the Number of Mosquitoes in and Around My Home?


The most important step is to eliminate potential breeding habitats for mosquitoes. Get rid of any standing water around the home, including water in potted plant dishes, garbage cans, old tires, gutters, ditches, wheelbarrows, bird baths, hollow trees, and wading pools. Any standing water should be drained, including abandoned or unused swimming pools. Mosquitoes can breed in any puddle that lasts more than 4 days. Make sure windows and screen doors are "bug tight." Replace outdoor lights with yellow "bug" lights. Wear headnets, long-sleeved shirts, and long pants if venturing into areas with high mosquito populations, such as salt marshes or wooded areas. Use mosquito repellents when necessary, always following label instructions.



Should I Take Steps to Reduce Exposure to Pesticides During Mosquito Control Spraying?

Generally, there is no need to relocate during mosquito control spraying. The pesticides have been evaluated for this use and found to pose minimal risks to human health and the environment when used according to label directions. For example, EPA has estimated the exposure and risks to both adults and children posed by ULV aerial and ground applications of the insecticides malathion and naled. For all the exposure scenarios considered, exposures ranged from 100 to 10,000 times below an amount of pesticide that might pose a health concern. These estimates assumed several spraying events over a period of weeks, and also assumed that a toddler would ingest some soil and grass in addition to dermal exposure. Other mosquito control pesticides pose similarly low risks. (For more details on health and environmental risk considerations, see the separate EPA fact sheets on the specific mosquito control pesticides.)

Although mosquito control pesticides pose low risks, some people may prefer to avoid or further minimize exposure. Some common sense steps to help reduce possible exposure to pesticides include:

• Pay attention to the local media for announcements about spraying and remain indoors during applications in the immediate area.

• People who suffer from chemical sensitivities or feel spraying may aggravate a preexisting health condition, may consult their physician or local health department and take special measures to avoid exposure.

• Close windows and turn off window-unit air conditioners when spraying is taking place in the immediate area.

• Do not let children play near or behind truck-mounted applicators when they are in use.

Where Can I Get More Information?

For more information about mosquito control in your area, contact your state or local health department. Other resources for information on public health, disease control, and mosquito control include the following:

Centers for Disease Control and Prevention (CDC)

Tel: 970-221-6400 Fax: 970-221-6476 E-mail: [email protected] Web site: http://www.cdc.gov

National Pesticide Information Center (NPIC)

Tel: 1-800-858-7378 E-mail: [email protected] Web site: http://npic.orst.edu/

West Nile Virus Resource Guide: http://npic.orst.edu/wnv/



http://www.cdc.gov/

http://npic.orst.edu/

http://npic.orst.edu/wnv/


American Mosquito Control Association (AMCA)

Joseph M. Conlon, Technical Advisor Tel/Fax: (904) 215-3008 E-mail: [email protected]

The EPA’s View of Larvicides for Mosquito Control The Environmental Protection Agency (EPA) evaluates and registers (licenses) pesticides to ensure that they can be used safely. These pesticides include products used in the mosquito control programs that states and communities have established. To evaluate any pesticide, EPA assesses a wide variety of tests to determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish and plants, including endangered species and non-target organisms.

Officials responsible for mosquito control programs make decisions to use pesticides based on an evaluation of the risks to the general public from diseases transmitted by mosquitoes or on an evaluation of the nuisance level that communities can tolerate from a mosquito infestation. Based on surveillance and monitoring, mosquito control officials select specific pesticides and other control measures that best suit local conditions in order to achieve effective control of mosquitoes with the least impact on human health and the environment. It is especially important to conduct effective mosquito prevention programs by eliminating breeding habitats or applying pesticides to control the early life stages of the mosquito. Prevention programs, such as elimination of any standing water that could serve as a breeding site, help reduce

Leon County Mosquito Control, Tallahassee, FL




the adult mosquito population and the need to apply other pesticides for adult mosquito control. Since no pesticide can be considered 100 percent safe, pesticide applicators and the general public should always exercise care and follow specified safety precautions during use to reduce risks. This fact sheet provides basic information on larvicides, a type of pesticide used in mosquito control programs.

What is the Mosquito Life Cycle?

The mosquito goes through four distinct stages during its life cycle:

• egg - hatches when exposed to water; • larva - (plural. - larvae) lives in the water; molts several times; most species

surface to breathe air; • pupa - (plural - pupae) does not feed; stage just prior to emerging as adult; • adult - flies short time after emerging and after its body parts have hardened.

What are Larvicides?

Larvicides kill mosquito larvae. Larvicides include biological insecticides, such as the microbial larvicides Bacillus sphaericus and Bacillus thuringiensis israelensis. Larvicides include other pesticides, such as temephos, methoprene, oils, and monomolecular films. Larvicide treatment of breeding habitats help reduce the adult mosquito population in nearby areas.

How are Larvicides Used in Mosquito Control?

State and local agencies in charge of mosquito control typically employ a variety of techniques in an Integrated Pest Management (IPM) program. An IPM approach includes surveillance, source reduction, larviciding and adulticiding to control mosquito populations. Since mosquitoes must have water to breed, source reduction can be as simple as turning over trapped water in a container to undertaking large-scale engineering and management of marsh water levels. Larviciding involves applying pesticides to breeding habitats to kill mosquito larvae. Larviciding can reduce overall pesticide usage in a control program. Killing mosquito larvae before they emerge as adults can reduce or eliminate the need for ground or aerial application of pesticides to kill adult mosquitoes.

What are Microbial Larvicides?

Microbial larvicides are bacteria that are registered as pesticides for control of mosquito larvae in outdoor areas such as irrigation ditches, flood water, standing ponds, woodland pools, pastures, tidal water, fresh or saltwater marshes, and storm water retention areas. Duration of effectiveness depends primarily on the mosquito species, the environmental



conditions, the formulation of the product, and water quality. Microbial larvicides may be used along with other mosquito control measures in an IPM program. Tmicrobial larvicides used for mosquito control are

he

ure

ti,

Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus (B. sphaericus).

Bacillus thuringiensis israelensis is a naturally occurring soil bacterium registered for control of mosquito larvae. Bti was first registered by EPA as an insecticide in 1983. Mosquito larvae eat the Bti product that is made up of the dormant spore form of the bacterium and an associated ptoxin. The toxin disrupts the gut in the mosquito by binding to receptor cells present in insects, but not in mammals. There are 26

Bti products registered for use in the United States. Aquabac, Teknar, Vectobac, and LarvX are examples of common trade names for the mosquito control products.

Bacillus sphaericus is a naturally occurring bacterium that is found throughout the world. B. sphaericus was initially registered by EPA in 1991 for use against various kinds of

mosquito larvae. Mosquito larvae ingest the bacteria, and as with B

maf

D

Teo

D

Es

-

Mosquitoes breed anyplace there’s water!
the toxin disrupts the gut in the
osquito by binding to receptor cells present in insects but not in mammals. VectoLex CG nd WDG are registered B. sphaericus products and are effective for approximately one to our weeks after application.

o Microbial Larvicides Pose Risks to Human Health?

he microbial pesticides have undergone extensive testing prior to registration. They are ssentially nontoxic to humans, so there are no concerns for human health effects with Bti r B. sphaericus when they are used according to label directions.

o Microbial Larvicides Pose Risks to Wildlife or the Environment?

xtensive testing shows that microbial larvicides do not pose risks to wildlife, nontarget pecies, or the environment, when used according to label directions.

West Nile Virus Guide ----------------------------------------------------------------------------------------------------------- ©All Rights Reserved www.WestNileVirusGuide.con Page - 50 -


What is Methoprene?

Methoprene is a compound first registered by EPA in 1975 that mimics the action of an insect growth-regulating hormone and prevents the normal maturation of insect larvae. It is applied to water to kill mosquito larvae, and it may be used along with other mosquito control measures in an IPM program. Altosid is the name of the methoprene product used in mosquito control and is applied as briquets (similar in form to charcoal briquets), pellets, sand granules, and liquids. The liquid and pelletized formulations can be applied by helicopter and fixed-wing aircraft.

Does Methoprene Pose Risks to Human Health?

Methoprene, used for mosquito control according to its label directions, does not pose unreasonable risks to human health. In addition to posing low toxicity to mammals, there is little opportunity for human exposure, since the material is applied directly to ditches, ponds, marshes, or flooded areas that are not drinking water sources.

Does Methoprene Pose Risks to Wildlife or the Environment?

Methoprene used in mosquito control programs does not pose unreasonable risks to wildlife or the environment. Toxicity of methoprene to birds and fish is low, and it is nontoxic to bees. Methoprene breaks down quickly in water and soil and will not leach into ground water. Methoprene mosquito control products present minimal acute and chronic risk to freshwater fish, freshwater invertebrates, and estuarine species.

What is Temephos?

Temephos is an organophosphate (OP) pesticide registered by EPA in 1965 to control mosquito larvae, and it is the only organophosphate with larvicidal use. It is an important resistance management tool for mosquito control programs; its use helps prevent mosquitoes from developing resistance to the bacterial larvicides. Temephos is used in areas of standing water, shallow ponds, swamps, marshes, and intertidal zones. It may be used along with other mosquito control measures in an IPM program. Abate is the trade name of the temephos product used for mosquito control. Temephos is applied most commonly by helicopter but can be applied by backpack sprayers, fixed-wing aircraft, and right-of-way sprayers in either liquid or granular form.

Does Temephos Pose Risks to Human Health?

Temephos, applied according to the label for mosquito control, does not pose unreasonable risks to human health. It is applied to water, and the amount of temephos is very small in relation to the area covered, less than 1 ounce of active ingredient per acre for the liquid and 8 ounces per acre for the granular formulations. Temephos breaks down within a few days in water, and post-application exposure is minimal. However, at high dosages, temephos, like other OPs, can overstimulate the nervous system causing nausea, dizziness, and confusion.



Does Temephos Pose Risks to Wildlife or the Environment?

Because temephos is applied directly to water, it is not expected to have a direct impact on terrestrial animals or birds. Current mosquito larviciding techniques pose some risk to nontarget aquatic species and the aquatic ecosystem. Although temephos presents relatively low risk to birds and terrestrial species, available information suggests that it is more toxic to aquatic invertebrates than alternative larvicides. For this reason, EPA is limiting temephos use to areas where less-hazardous alternatives would not be effective, specifying intervals between applications, and limiting the use of high application rates.

What is the Current Regulatory Status of Temephos?

As part of its responsibility to reassess all older pesticides registered before 1984, EPA completed its revised risk assessments for temephos in July 2001, and has issued risk management decisions in the final reregistration eligibility decision (RED). The RED document is available on the EPA Web site at: www.epa.gov/oppsrrd1/REDs/temephos_red.htm.

What are Monomolecular Films?

Monomolecular films are low-toxicity pesticides that spread a thin film on the surface of the water that makes it difficult for mosquito larvae, pupae, and emerging adults to attach to the water's surface, causing them to drown. Films may remain active typically for 10-14 days on standing water, and have been used in the United States in floodwaters, brackish waters, and ponds. They may be used along with other mosquito control measures in an IPM program. They are also known under the trade names Arosurf MSF and Agnique MMF.

Do Monomolecular Films Pose Risks to Human Health?

Monomolecular films, used according to label directions for larva and pupa control, do not pose a risk to human health. In addition to low toxicity, there is little opportunity for human exposure, since the material is applied directly to ditches, ponds, marshes, or flooded areas that are not drinking water sources.

Do Films Pose Risks to Wildlife or the Environment?

Monomolecular films, used according to label directions for larva and pupa control, pose minimal risks to the environment. They do not last very long in the environment, and are usually applied only to standing water, such as roadside ditches, woodland pools, or containers which contain few nontarget organisms.


http://www.epa.gov/oppsrrd1/REDs/temephos_red.htm


What are Oils?

Oils, like films, are pesticides used to form a coating on top of water to drown larvae, pupae, and emerging adult mosquitoes. They are specially derived from petroleum distillates and have been used for many years in the United States to kill aphids on crops and orchard trees, and to control mosquitoes. They may be used along with other mosquito control measures in an IPM program. Trade names for oils used in mosquito control are Bonide, BVA2, and Golden Bear-1111, (GB-1111).

Do Oils Pose Risks to Human Health?

Oils, used according to label directions for larva and pupa control, do not pose a risk to human health. In addition to low toxicity, there is little opportunity for human exposure, since the material is applied directly to ditches, ponds, marshes, or flooded areas that are not drinking water sources.

Do Oils Pose Risks to Wildlife or the Environment?

Oils, if misapplied, may be toxic to fish and other aquatic organisms. For that reason, EPA has established specific precautions on the label to reduce such risks.

Information on Arboviral Encephalitides Although our discussion and investigation of mosquitoes is centered around the west nile virus, mosquitoes are responsible for a known variety of viral illnesses. We will take a brief look at what is known today.

Perspectives

Arthropod-borne viruses, i.e., arboviruses, are viruses that are maintained in nature through biological transmission between susceptible vertebrate hosts by blood feeding arthropods (mosquitoes, psychodids, ceratopogonids, and ticks). Vertebrate infection occurs when the infected arthropod takes a blood meal. The term 'arbovirus' has no taxonomic significance. Arboviruses that cause human encephalitis are members of three virus families: the Togaviridae (genus Alphavirus), Flaviviridae, and Bunyaviridae.

All arboviral encephalitides are zoonotic, being maintained in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector. These cycles usually remain undetected until humans encroach on a natural focus, or the virus escapes this focus via a secondary vector or vertebrate host as the result of some ecologic change. Humans and domestic animals can develop clinical illness but usually are "dead-end" hosts because they do not produce significant viremia, and do not contribute to the transmission cycle. Many arboviruses that cause encephalitis have a variety of different vertebrate hosts and some are transmitted by more than one vector. Maintenance of the viruses in nature may be facilitated by vertical transmission (e.g., the virus is transmitted from the female through the eggs to the offspring).


http://www.cdc.gov/ncidod/dvbid/arbor/alphavir.htm

http://www.cdc.gov/ncidod/dvbid/arbor/schemat.htm


Arboviral encephalitides have a global distribution, but there are four main virus agents of encephalitis in the United States: eastern equine encephalitis (EEE), western equine encephalitis (WEE), St. Louis encephalitis (SLE) and La Crosse (LAC) encephalitis, all of which are transmitted by mosquitoes. Another virus, Powassan, is a minor cause of encephalitis in the northern United States, and is transmitted by ticks. A new Powassan-like virus has recently been isolated from deer ticks. Its relatedness to Powassan virus and its ability to cause disease has not been well documented. Most cases of arboviral encephalitis occur from June through September, when arthropods are most active. In milder (i.e., warmer) parts of the country, where arthropods are active late into the year, cases can occur into the winter months.

The majority of human infections are asymptomatic or may result in a nonspecific flu-like syndrome. Onset may be insidious or sudden with fever, headache, myalgias, malaise and occasionally prostration. Infection may, however, lead to encephalitis, with a fatal outcome or permanent neurologic sequelae. Fortunately, only a small proportion of infected persons progress to frank encephalitis.

Experimental studies have shown that invasion of the central nervous system (CNS), generally follows initial virus replication in various peripheral sites and a period of viremia. Viral transfer from the blood to the CNS through the olfactory tract has been suggested. Because the arboviral encephalitides are viral diseases, antibiotics are not effective for treatment and no effective antiviral drugs have yet been discovered. Treatment is supportive, attempting to deal with problems such as swelling of the brain, loss of the automatic breathing activity of the brain and other treatable complications like bacterial pneumonia.

There are no commercially available human vaccines for these U.S. diseases. There is a Japanese encephalitis vaccine available in the U.S. A tick-borne encephalitis vaccine is available in Europe. An equine vaccine is available for EEE, WEE and Venezuelan equine encephalitis (VEE). Arboviral encephalitis can be prevented in two major ways: personal protective measures and public health measures to reduce the population of infected mosquitoes. Personal measures include reducing time outdoors particularly in early evening hours, wearing long pants and long sleeved shirts and applying mosquito repellent to exposed skin areas. Public health measures often require spraying of insecticides to kill juvenile (larvae) and adult mosquitoes.

Selection of mosquito control methods depends on what needs to be achieved; but, in most emergency situations, the preferred method to achieve maximum results over a wide area is aerial spraying. In many states aerial spraying may be available in certain locations as a means to control nuisance mosquitoes. Such resources can be redirected to areas of virus activity. When aerial spraying is not routinely used, such services are usually contracted for a given time period.

Financing of aerial spraying costs during large outbreaks is usually provided by state emergency contingency funds. Federal funding of emergency spraying is rare and almost always requires a federal disaster declaration. Such disaster declarations usually occur when the vector-borne disease has the potential to infect large numbers of people, when a large population is at risk and when the area requiring treatment is extensive. Special large planes maintained by the United States Air Force can be called upon to deliver the insecticide(s) chosen for such emergencies. Federal disaster declarations have relied heavily on risk assessment by the CDC.

Laboratory diagnosis of human arboviral encephalitis has changed greatly over the last few years. In the past, identification of antibody relied on four tests: hemagglutination-inhibition, complement fixation, plaque reduction neutralization test, and the indirect fluorescent antibody (IFA) test. Positive identification using these immunoglobulin M (IgM) - and IgG-based assays requires a four-fold increase in titer between acute and convalescent serum samples. With the advent of solid-phase antibody-binding assays, such as enzyme-linked immunosorbent assay (ELISA), the diagnostic algorithm for identification of viral activity has changed. Rapid serologic assays such as


http://www.cdc.gov/ncidod/dvbid/arbor/worldist.htm


IgM-capture ELISA (MAC-ELISA) and IgG ELISA may now be employed soon after infection. Early in infection, IgM antibody is more specific, while later in infection, IgG antibody is more reactive. Inclusion of monoclonal antibodies (MAbs) with defined virus specificities in these solid phase assays has allowed for a level of standardization that was not previously possible.

Virus isolation and identification have also been useful in defining viral agents in serum, cerebrospinal fluid and mosquito vectors. While virus isolation still depends upon growth of an unknown virus in cell culture or neonatal mice, virus identification has also been greatly facilitated by the availability of virus-specific MAbs for use in IFA assays. Similarly, MAbs with avidities sufficiently high to allow for specific binding to virus antigens in a complex protein mixture (e.g., mosquito pool suspensions) have enhanced our ability to rapidly identify virus agents in situ. While polymerase chain reaction (PCR) has been developed to identify a number of viral agents, such tests have not yet been validated for routine rapid identification in the clinical setting.

Mosquito-borne encephalitis offers a rare opportunity in public health to detect the risk of a disease before it occurs and to intervene to reduce that risk substantially. The surveillance required to detect risk is being increasingly refined by the potential utilization of these new technologies which allows for rapid identification of dangerous viruses in mosquito populations. These rapid diagnostic techniques used in threat recognition can shorten public health response time and reduce the geographic spread of infected vectors and thereby the cost of containing them. The Arbovirus Diseases Branch of NCID's Division of Vector-Borne Infectious Diseases has responsibility for CDC's programs in surveillance, diagnosis, research and control of arboviral encephalitides.

La Crosse Encephalitis

La Crosse (LAC) encephalitis was discovered in La Crosse, Wisconsin in 1963. Since then, the virus has been identified in several Midwestern and Mid-Atlantic states. During an average year, about 75 cases of LAC encephalitis are reported to the CDC. Most cases of LAC encephalitis occur in children under 16 years of age. LAC virus is a Bunyavirus and is a zoonotic pathogen cycled between the daytime-biting treehole mosquito, Aedes triseriatus, and vertebrate amplifier hosts (chipmunks, tree squirrels) in deciduous forest habitats. The virus is maintained over the winter by transovarial transmission in mosquito eggs. If the female mosquito is infected, she may lay eggs that carry the virus, and the adults coming from those eggs may be able to transmit the virus to chipmunks and to humans.

Historically, most cases of LAC encephalitis occur in the upper Midwestern states (Minnesota, Wisconsin, Iowa, Illinois, Indiana, and Ohio). Recently, more cases are being reported from states in the mid-Atlantic (West Virginia, Virginia and North Carolina) and southeastern (Alabama and Mississippi) regions of the country. It has long been suspected that LAC encephalitis has a broader distribution and a higher incidence in the eastern United States, but is under-reported because the etiologic agent is often not specifically identified.

LAC encephalitis initially presents as a nonspecific summertime illness with fever, headache, nausea, vomiting and lethargy. Severe disease occurs most commonly in children under the age of 16 and is characterized by seizures, coma, paralysis, and a variety of neurological sequelae after recovery. Death from LAC encephalitis occurs in less than 1% of clinical cases. In many clinical settings, pediatric cases presenting with CNS involvement are routinely screened for herpes or enteroviral etiologies. Since there is no specific treatment for LAC encephalitis, physicians often do not request the tests required to specifically identify LAC virus, and the cases are reported as aseptic meningitis or viral encephalitis of unknown etiology.

Also found in the United States, Jamestown Canyon and Cache Valley viruses are related to LAC, but rarely cause encephalitis.



Eastern Equine Encephalitis

Eastern equine encephalitis (EEE) is also caused by a virus transmitted to humans and equines by the bite of an infected mosquito. EEE virus is an alphavirus that was first identified in the 1930's and currently occurs in focal locations along the eastern seaboard, the Gulf Coast and some inland Midwestern locations of the United States. While small outbreaks of human disease have occurred in the United States, equine epizootics can be a common occurrence during the summer and fall.

It takes from 4-10 days after the bite of an infected mosquito for an individual to develop symptoms of EEE. These symptoms begin with a sudden onset of fever, general muscle pains, and a headache of increasing severity. Many individuals will progress to more severe symptoms such as seizures and coma. Approximately one-third of all people with clinical encephalitis caused by EEE will die from the disease and of those who recover, many will suffer permanent brain damage with many of those requiring permanent institutional care.

In addition to humans, EEE virus can produce severe disease in: horses, some birds such as pheasants, quail, ostriches and emus, and even puppies. Because horses are outdoors and attract hordes of biting mosquitoes, they are at high risk of contracting EEE when the virus is present in mosquitoes. Human cases are usually preceded by those in horses and exceeded in numbers by horse cases which may be used as a surveillance tool.

EEE virus occurs in natural cycles involving birds and Culiseta melanura, in some swampy areas nearly every year during the warm months. Where the virus resides or how it survives in the winter is unknown. It may be introduced by migratory birds in the spring or it may remain dormant in some yet undiscovered part of its life cycle. With the onset of spring, the virus reappears in the birds (native bird species do not seem to be affected by the virus) and mosquitoes of the swamp. In this usual cycle of transmission, virus does not escape from these areas because the mosquito involved prefers to feed upon birds and does not usually bite humans or other mammals.

For reasons not fully understood, the virus may escape from enzootic foci in swamp areas in birds or bridge vectors such as Coquilletidia perturbans and Aedes sollicitans. These species feed on both birds and mammals and can transmit the virus to humans, horses, and other hosts. Other mosquito species such as Ae. vexans and Culex nigripalpus can also transmit EEE virus. When health officials maintain surveillance for EEE virus activity, this movement out of the swamp can be detected, and if the level of activity is sufficiently high, can recommend and undertake measures to reduce the risk to humans.

Western Equine Encephalitis

The alphavirus western equine encephalitis (WEE) was first isolated in California in 1930 from the brain of a horse with encephalitis, and remains an important cause of encephalitis in horses and humans in North America, mainly in western parts of the USA and Canada. In the western United States, the enzootic cycle of WEE involves passerine birds, in which the infection is inapparent, and culicine mosquitoes, principally Cx. tarsalis, a species that is associated with irrigated agriculture and stream drainages. The virus has also been isolated from a variety of mammal species. Other important mosquito vector species include Aedes melanimon in California, Ae. dorsalis in Utah and New Mexico and Ae. campestris in New Mexico. WEE virus was isolated from field collected larvae of Ae. dorsalis, providing evidence that vertical transmission may play an important role in the maintenance cycle of an alphavirus.

Expansion of irrigated agriculture in the North Platte River Valley during the past several decades has created habitats and conditions favorable for increases in populations of granivorous birds such as the house sparrow, Passer domesticus, and mosquitoes such as Cx. tarsalis, Aedes dorsalis and


http://www.cdc.gov/ncidod/dvbid/arbor/alphavir.htm


Aedes melanimon. All of these species may play a role in WEE virus transmission in irrigated areas. In addition to Cx. tarsalis, Ae. dorsalis and Ae. melanimon, WEE virus also has been isolated occasionally from some other mosquito species present in the area. Two confirmed and several suspect cases of WEE were reported from Wyoming in 1994. In 1995, two strains of WEE virus were isolated from Culex tarsalis and neutralizing antibody to WEE virus was demonstrated in sera from pheasants and house sparrows. During 1997, 35 strains of WEE virus were isolated from mosquitoes collected in Scotts Bluff County, Nebraska.

Human WEE cases are usually first seen in June or July. Most WEE infections are asymptomatic or present as mild, nonspecific illness. Patients with clinically apparent illness usually have a sudden onset with fever, headache, nausea, vomiting, anorexia and malaise, followed by altered mental status, weakness and signs of meningeal irritation. Children, especially those under 1 year old, are affected more severely than adults and may be left with permanent sequelae, which is seen in 5 to 30% of young patients. The mortality rate is about 3%.

St. Louis Encephalitis

In the United States, the leading cause of epidemic flaviviral encephalitis is St. Louis encephalitis (SLE) virus. SLE is the most common mosquito-transmitted human pathogen in the U.S. While periodic SLE epidemics have occurred only in the Midwest and southeast, SLE virus is distributed throughout the lower 48 states. Since 1964, there have been 4,437 confirmed cases of SLE with an average of 193 cases per year (range 4 - 1,967). However, less than 1% of SLE viral infections are clinically apparent and the vast majority of infections remain undiagnosed. Illness ranges in severity from a simple febrile headache to meningoencephalitis, with an overall case-fatality ratio of 5-15 %. The disease is generally milder in children than in adults, but in those children who do have disease, there is a high rate of encephalitis. The elderly are at highest risk for severe disease and death. During the summer season, SLE virus is maintained in a mosquito-bird-mosquito cycle, with periodic amplification by peridomestic birds and Culex mosquitoes. In Florida, the principal vector is Cx. nigripalpus, in the Midwest, Cx. pipiens pipiens and Cx. p. quinquefasciatus and in the western United States, Cx. tarsalis and members of the Cx. pipiens complex.

Powassan Encephalitis

Powassan (POW) virus is a flavivirus and currently the only well documented tick-borne transmitted arbovirus occurring in the United States and Canada. Recently a Powassan-like virus was isolated from the deer tick, Ixodes scapularis. Its relationship to POW and its ability to cause human disease has not been fully elucidated. POW's range in the United States is primarily in the upper tier States. In addition to isolations from man, the virus has been recovered from ticks (Ixodes marxi, I. cookei and Dermacentor andersoni) and from the tissues of a skunk (Spiligale putorius). It is a rare cause of acute viral encephalitis. POW virus was first isolated from the brain of a 5-year-old child who died in Ontario in 1958. Patients who recover may have residual neurological problems.

Venezuelan Equine Encephalitis

Like EEE and WEE viruses, Venezuelan equine encephalitis (VEE) is an alphavirus and causes encephalitis in horses and humans and is an important veterinary and public health problem in Central and South America. Occasionally, large regional epizootics and epidemics can occur resulting in thousands of equine and human infections. Epizootic strains of VEE virus can infect and be transmitted by a large number of mosquito species. The natural reservoir host for the epizootic strains is not known. A large epizootic that began in South America in 1969 reached Texas in 1971. It was estimated that over 200,000 horses died in that outbreak, which was controlled by a massive equine vaccination program using an experimental live attenuated VEE vaccine. There were several thousand human infections. A more recent VEE epidemic occurred in the fall of 1995 in



Venezuela and Colombia with an estimated 90,000 human infections. Infection of man with VEE virus is less severe than with EEE and WEE viruses, and fatalities are rare. Adults usually develop only an influenza-like illness, and overt encephalitis is usually confined to children. Effective VEE virus vaccines are available for equines.

Enzootic strains of VEE virus have a wide geographic distribution in the Americas. These viruses are maintained in cycles involving forest dwelling rodents and mosquito vectors, mainly Culex (Melanoconion) species. Occasional cases or small outbreaks of human disease are associated with there viruses, the most recent outbreaks were in Venezuela in 1992, Peru in 1994 and Mexico in 1995-96.

Other Arboviral Encephalitides

Many other arboviral encephalitides occur throughout the world. Most of these diseases are problems only for those individuals traveling to countries where the viruses are endemic.

Japanese Encephalitis

Japanese encephalitis (JE) virus is a flavivirus, related to SLE, and is widespread throughout Asia. Worldwide, it is the most important cause of arboviral encephalitis with over 45,000 cases reported annually. In recent years, JE virus has expanded its geographic distribution with outbreaks in the Pacific. Epidemics occur in late summer in temperate regions, but the infection is enzootic and occurs throughout the year in many tropical areas of Asia. The virus is maintained in a cycle involving culicine mosquitoes and waterbirds. The virus is transmitted to man by Culex mosquitoes, primarily Cx. tritaeniorhynchus, which breed in rice fields. Pigs are the main amplifying hosts of JE virus in peridomestic environments.

The incubation period of JE is 5 to 14 days. Onset of symptoms is usually sudden, with fever, headache and vomiting. The illness resolves in 5 to 7 days if there is no CNS involvement. The mortality in most outbreaks is less than 10%, but is higher in children and can exceed 30%. Neurologic sequelae in patients who recover are reported in up to 30% of cases. A formalin-inactivated vaccine prepared in mice is used widely in Japan, China, India, Korea, Taiwan and Thailand. This vaccine is currently available for human use in the United States, for individuals who might be traveling to endemic countries.

Tick-Borne Encephalitis

Tick-borne encephalitis (TBE) is caused by two closely related flaviviruses which are distinct biologically. The eastern subtype causes Russian spring-summer encephalitis (RSSE) and is transmitted by Ixodes persulcatus, whereas the western subtype is transmitted by Ixodes ricinus and causes Central European encephalitis (CEE). The name CEE is somewhat misleading, since the condition can occur throughout much of Europe. Of the two subtypes, RSSE is the more severe infection, having a mortality of up to 25% in some outbreaks, whereas mortality in CEE seldom exceeds 5%.

The incubation period is 7 to 14 days. Infection usually presents as a mild, influenza-type illness or as benign, aseptic meningitis, but may result in fatal meningoencephalitis. Fever is often biphasic, and there may be severe headache and neck rigidity, with transient paralysis of the limbs, shoulders or less commonly the respiratory musculature. A few patients are left with residual paralysis. Although the great majority of TBE infections follow exposure to ticks, infection has occurred through the ingestion of infected cows' or goats' milk. An inactivated TBE vaccine is currently available in Europe and Russia.



West Nile Encephalitis

WNV is a flavivirus belonging taxonomically to the Japanese encephalitis serocomplex that includes the closely related St. Louis encephalitis (SLE) virus, Kunjin and Murray Valley encephalitis viruses, as well as others. WNV was first isolated in the West Nile Province of Uganda in 1937 (2). The first recorded epidemics occurred in Israel during 1951-1954 and in 1957. Epidemics have been reported in Europe in the Rhone delta of France in 1962 and in Romania in 1996 (3-5). The largest recorded epidemic occurred in South Africa in 1974 (6).

An outbreak of arboviral encephalitis in New York City and neighboring counties in New York state in late August and September 1999, was initially attributed to St. Louis encephalitis virus based on positive serologic findings in cerebrospinal fluid (CSF) and serum samples using a virus-specific IgM-capture enzyme-linked immunosorbent assay (ELISA). The outbreak has been subsequently confirmed as caused by West Nile virus based on the identification of virus in human, avian, and mosquito samples. See also these MMWR articles Outbreak of West Nile-Like Viral Encephalitis -- New York, 1999. MMWR, 1999:48(38);845-9 and Update: West Nile-Like Viral Encephalitis -- New York, 1999. MMWR, 1999:48(39);890-2. A recent outbreak WN encephalitis occurred in Bucharest, Romania in 1996.

The virus that caused the New York area outbreak has been definitively identified as a strain of WNV. The genomic sequences identified to date from human brain, virus isolates from zoo birds, dead crows, and mosquito pools are identical. SLE and West Nile viruses are antigenically related, and cross reactions are observed in most serologic tests. The isolation of viruses and genomic sequences from birds, mosquitoes, and human brain tissue permitted the discovery of West Nile virus in North America and prompted more specific testing. The limitations of serologic assays emphasize the importance of isolating the virus from entomologic, clinical, or veterinary material.

Although it is not known when and how West Nile virus was introduced into North America, international travel of infected persons to New York or transport by imported infected birds may have played a role. WNV can infect a wide range of vertebrates; in humans it usually produces either asymptomatic infection or mild febrile disease, but can cause severe and fatal infection in a small percentage of patients. Within its normal geographic distribution of Africa, the Middle East, western Asia, and Europe, WNV has not been documented to cause epizootics in birds; crows and other birds with antibodies to WNV are common, suggesting that asymptomatic or mild infection usually occurs among birds in those regions. Similarly, substantial bird virulence of SLE virus has not been reported. Therefore, an epizootic producing high mortality in crows and other bird species is unusual for either WNV or SLE virus. For both viruses, migratory birds may play an important role in the natural transmission cycles and spread. Like SLE virus, WNV is transmitted principally by Culex species mosquitoes, but also can be transmitted by Aedes, Anopheles, and other species. The predominance of urban Culex pipiens mosquitoes trapped during this outbreak suggests an important role for this species. Enhanced surveillance for early detection of virus activity in birds and mosquitoes will be crucial to guide control measures.

West Nile Encephalitis References

See the West Nile Virus Publications page.

Murray Valley Encephalitis

Murray Valley encephalitis (MVE) is endemic in New Guinea and in parts of Australia; and is related to SLE, WN and JE viruses. Inapparent infections are common, and the small number of fatalities have mostly been in children.


http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/mm4838a1.htm




http://www.cdc.gov/ncidod/dvbid/westnile/publications.htm


Questions & Answers

Questions and Answers About West Nile

Compiled by the Center For Disease and Control

We've put together a selection of answers to the questions people ask most about West Nile virus and West Nile virus encephalitis. They are arranged by topic and are updated regularly.

Please select a topic from the list below:

• Overview • Statistics on WNV Human Cases • Understanding West Nile Virus Human Case Count Numbers • Questions about Dead Birds • Who is at Risk? • Transmission • Symptoms • West Nile Virus and Poliomyelitis • Preventing West Nile Virus infection • Updated! Insect Repellent Use and Safety • Vaccine • Testing and Treatment • West Nile Virus, Pregnancy and Breastfeeding • Blood Transfusion, Organ Donation and Blood Donation Screening Information • Pesticides Used for Mosquito Control • West Nile Virus and Dogs and Cats • West Nile Virus and Horses • West Nile Virus and Squirrels • West Nile Virus and Wild Game/Meat • Additional Information



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http://www.cdc.gov/ncidod/dvbid/westnile/qa/symptoms.htm

http://www.cdc.gov/ncidod/dvbid/westnile/qa/Poliomyelitis.htm



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Overview of West Nile Virus Q: What is West Nile virus? A. West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus which is also found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals

Q. What are West Nile encephalitis, West Nile meningitis and “neuroinvasive disease” and West Nile fever? A. The most severe type of disease due to a person being infected with West Nile virus is sometimes called “neuroinvasive disease” because it affects a person’s nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks.

Q. Historically, where has West Nile encephalitis occurred worldwide? A. See the map describing distribution of flaviviruses, including West Nile virus:


Q. How long has West Nile virus been in the U.S.? A. It is not known how long it has been in the U.S., but CDC scientists believe the virus has probably been in the eastern U.S. since the early summer of 1999, possibly longer.

Q. I understand West Nile virus was found in "overwintering" mosquitoes in the New York City area in early 2000. What does this mean? A. One of the species of mosquitoes found to carry West Nile virus is the Culex species which survive through the winter, or "overwinter," in the adult stage. That the virus survived along with the mosquitoes was documented by the widespread transmission the summer of 2000.

View enlarged image.

Q. Is West Nile virus now established in the Western Hemisphere? A. The continued expansion of West Nile virus in the United States indicates that it is permanently established in the Western Hemisphere.

Q. Is the disease seasonal in its occurrence? A. In the temperate zone of the world (i.e., between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.


http://www.cdc.gov/ncidod/dvbid/westnile/map.htm


Cases of West Nile Human Disease Q. How many cases of West Nile disease in humans have occurred in the U.S.? A. Our Statistics, Surveillance, and Control page contains maps showing the distribution of West Nile virus-related human disease cases, by state, in the U.S. in 2004.

Please see CDC's current case count for the number and nature of human cases of West Nile virus-related disease reported in the U.S. in 2004.

In 2003, there were 9862 human cases of WNV disease reported, including 264 deaths. For a report of cases by clinical syndrome and by state, please see the 2003 human disease cases.

In 2002, there were 4156 human cases of WNV disease, including 284 deaths. Cases were reported throughout much of the US; for a report of cases by each state please refer to the 2002 human case count. In 2001, there were 66 human cases of severe disease and 9 deaths. In 2000, 21 cases were reported, including 2 deaths in the New York City area. In 1999, 62 cases of severe disease, including 7 deaths, occurred in the New York area.

There are no reliable estimates are available for the number of cases of West Nile encephalitis that occur worldwide.

Q. What proportion of people with severe illness due to West Nile virus die? A. Among those with severe illness due to West Nile virus, case-fatality rates range from 3% to 15% and are highest among the elderly. Less than 1% of people who become infected with West Nile virus will develop severe illness -- most people who get infected do not develop any disease at all.






http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount2002.htm


Understanding the Numbers Posted for West Nile Virus Cases

Q. Why do the media, my state health department, and the CDC sometimes report different statistics on the number of human West Nile virus cases? A. The CDC human case count, as reported in our ArboNET Surveillance System, is based on the number of West Nile virus cases that have been officially reported by each state health department to CDC. Before a state makes its report to CDC, follow-up laboratory testing is often conducted. CDC believes it is important to report the most accurate information possible, so our numbers may be lower than those reported in the media until official case reports are received from the states.

As West Nile virus has become more familiar in the US, many private labs are now able to do early testing on suspected human cases of disease. Physicians often send samples to private labs in order to get quick preliminary results to know if they need to look for another source of illness that may need treatment. Some states and often the media may incorporate these early test results in their total case count.

Q. How are human cases of WNV diagnosed? A. West Nile virus (WNV) infection can be suspected in a person based on clinical symptoms and patient history. Laboratory testing is required for a confirmed diagnosis.

The most commonly used WNV laboratory test measures antibodies that that are produced very early in the infected person. These antibodies, called IgM antibodies, can be measured in blood or cerebrospinal fluid (CSF), which is the fluid surrounding the brain and spinal cord. This blood test may not be positive when symptoms first occur; however, the test is positive in most infected people within 8 days of onset of symptoms.

A test for WNV IgM-antibody is used by CDC, state and local public health labs and increasingly at private laboratories When testing is conducted at private laboratories the health department or CDC will often confirm results in their own laboratories before officially reporting WNV cases.

In some instances, health departments may conduct or request additional testing before officially reporting a case to CDC's Arbonet Surveillance System. The state or the CDC reference laboratory may repeat the initial IgM-antibody testing.

A state may also perform or ask CDC to perform an additional, different test on a specimen. This latter test (plaque reduction neutralization test - PRNT) is usually performed when:

• the state finds its initial case(s) of human WNV illness • IgM results are not definitive due to equivocal laboratory testing results or

insufficient specimens • the patient might have been exposed to other closely related viruses (like St.

Louis encephalitis virus) which may result in a "false" positive laboratory test for WNV



These additional tests require growth of the virus and may take a week or longer (plus shipping time) to conduct. The results from the PRNT are often needed before CDC considers a human WNV infection confirmed.

Q. How does CDC decide when to report a case of WNV? A. CDC reports a case of WNV infection once a state officially reports that case to CDC.

The timing of the official report to CDC, relative to onset of symptoms in a person, is variable and depends on when an individual first seeks medical care and the extent of the laboratory testing, as described above, that the state determines is necessary before reporting.

At any given time, in addition to the official case count reported by CDC, there may be additional suspect cases under investigation or in various stages of testing, including supplemental or confirmatory laboratory testing.

Q. How many of the human WNV cases are being confirmed by the CDC laboratories? A. When WNV was first found in the United States in 1999, the CDC reference laboratory confirmed all human cases of WNV. Through a comprehensive CDC-sponsored laboratory training program, most states are now able to perform the initial blood tests to identify IgM antibodies in the blood or CSF of suspect human WNV infections, and many state laboratories are also able to perform the more involved PRNT. The CDC reference lab is called upon for confirmatory testing by fewer and fewer states; although the increased activity of WNV still require that many tests be performed at the CDC reference laboratory.



West Nile Virus and Dead Birds Q. What should I do if I find a dead bird? A. Check with with your local or state health department for instructions on reporting and diposing of a dead bird. If you need to pick up a dead bird, or local authorities tell you to simply dispose of it: Avoid bare-handed contact with any dead animals, and use gloves or an inverted plastic bag to place the bird carcass in a garbage bag and dispose of it with your routine trash. Q. Do birds infected with West Nile virus die or become ill? A. In the 1999 New York area epidemic, there was a large die-off of American crows. Since then, West Nile virus has been identified in more than 200 species of birds found dead in the United States. Most of these birds were identified through reporting of dead birds by the public.

Q. How can I report a sighting of dead bird(s) in my area? A. State and local health departments start collecting reports of dead birds at different times in the year. Some wait until the weather becomes warm before initiating their surveillance (disease monitoring) program. For information about reporting dead birds in your specific area, please contact your state or local health department.

Q. Why do some areas stop collecting dead birds? A. Some states and jurisdictions are no longer collecting dead birds because they have sufficiently established that the virus is in an area, and additional testing will not reveal any more information. Shifting resources away from testing of dead birds allows those resources to be devoted elsewhere in surveillance and control.

Who's at Risk for West Nile Virus Q. Who is at risk for getting West Nile encephalitis? A. All residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis; persons over 50 years of age have the highest risk of severe disease. It is unknown if immunocompromised persons are at increased risk for WNV disease.







Transmission Q. How do people get infected with West Nile virus (WNV)? A. The main route of human infection with West Nile virus is through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. The virus eventually gets into the mosquito's salivary glands. During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness.

Additional routes of human infection became apparent during the 2002 West Nile epidemic. It is important to note that these other methods of transmission represent a very small proportion of cases. Investigations have identified WNV transmission through transplanted organs and through blood transfusions. See Blood Transfusions and Transmission: Questions and Answers.

There is one reported case of transplacental (mother-to-child) WNV transmission. This case is detailed in MMWR Dec 20, 2002. There is also one reported case of transmission of WNV through breast-milk. See Questions and Answers concerning WNV and breastfeeding for more information on this topic. Although transmission of WNV and similar viruses to laboratory workers is not a new phenomenon, two recent cases of WNV infection of laboratory workers have been reported. These cases are detailed in MMWR Dec 20, 2002.

Q. What is the basic transmission cycle of West Nile virus? A. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito's salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness.

View enlarged image. Q. If I live in an area where birds or mosquitoes with West Nile virus have been reported and a mosquito bites me, am I likely to get sick? A. No. Even in areas where the virus is circulating, very few mosquitoes are infected with the virus. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.

Q. Can you get West Nile encephalitis from another person? A. No. West Nile encephalitis is NOT transmitted from person-to-person. For example, you cannot get West Nile virus from touching or kissing a person who has the disease, or from a health care worker who has treated someone with the disease.




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Q. Is a woman's pregnancy at risk if she gets infected with West Nile virus? A. There is one documented case of transplacental (mother-to-child) transmission of WNV in a human. Although the newborn in this case was infected with WNV at birth and had severe medical problems, it is unknown whether the WNV infection itself caused these problems or whether they were coincidental. More research will be needed to improve our understanding of the relationship - if any - between WNV infection and adverse birth outcomes.

Nevertheless, pregnant women should take precautions to reduce their risk for WNV and other arboviral infections by avoiding mosquitoes, using protective clothing, and using repellents containing DEET (See Using Repellent Safely). When WNV transmission is occurring in an area, pregnant women who become ill should see their health care provider, and those whose illness is consistent with acure WNV infection, should undergo appropriate diagnostic testing.

See MMWR Dec 20, 2002 for more information.

Q. Can West Nile virus be transmitted through blood transfusions? A. Please refer to Blood Transfusions and Transmission: Questions and Answers.

Q. Besides mosquitoes, can you get West Nile virus directly from other insects or ticks? A. Infected mosquitoes are the primary source for West Nile virus. Although ticks infected with West Nile virus have been found in Asia and Africa, their role in the transmission and maintenance of the virus is uncertain. However, there is no information to suggest that ticks played any role in the cases identified in the United States.

Q. How many types of animals have been found to be infected with West Nile virus? A. Although the vast majority of infections have been identified in birds, WN virus has been shown to infect horses, cats, bats, chipmunks, skunks, squirrels, and domestic rabbits.

Q. Can you get West Nile virus directly from birds? A. There is no evidence that a person can get the virus from handling live or dead infected birds. However, persons should avoid bare-handed contact when handling any dead animals and use gloves or double plastic bags to place the carcass in a garbage can.

Q. Can you get infected with West Nile virus by caring for an infected horse? A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of West Nile virus. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.

Q. Can you get WNV from eating game birds or animals that have been infected? A. There is no evidence that WNV virus can be transmitted to humans through consuming infected birds or animals. In keeping with overall public health practice,






and due to the risk of known food-borne pathogens, people should always follow procedures for fully cooking meat from either birds or mammals.

Q. How does West Nile virus actually cause severe illness and death in humans? A. Following transmission by an infected mosquito, West Nile virus multiplies in the person's blood system and crosses the blood-brain barrier to reach the brain. The virus interferes with normal central nervous system functioning and causes inflammation of brain tissue.

Q. How long does the West Nile virus remain in a person’s body after they are infected? A. There is no scientific evidence indicating that people can be chronically infected with West Nile virus. What remain in a person’s body for long periods of time are antibodies and “memory” white blood cells (T-lymphocytes) that the body produces to the virus. These antibodies and T-lymphocytes last for years, and may last for the rest of a person’s life. Antibodies are what many diagnostic tests look for when clinical laboratories testing is performed. Both antibodies and “memory” T-lymphocytes provide future protection from the virus.

Q. If a person contracts West Nile virus, does that person develop a natural immunity to future infection by the virus? A. It is assumed that immunity will be lifelong; however, it may wane in later years.

See Also –

• West Nile Virus and Dogs and Cats • West Nile Virus and Horses • West Nile Virus and Birds • West Nile Virus and Wild Game Hunters


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http://www.cdc.gov/ncidod/dvbid/westnile/qa/wnv_hunters.htm


Symptoms of West Nile Virus Updated! 8/16/2004

Q. What are the symptoms of West Nile virus (WNV) infection? A. Infection with WNV can be asymptomtic (no symptoms), or can lead to West Nile fever or severe West Nile disease.

It is estimated that about 20% of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands. While the illness can be as short as a few days, even healthy people have reported being sick for several weeks.

Worried about a mosquito bite? Reduce your stress and learn how to avoid them in the future:

• Use Repellent • Mosquito-Proof Your

Home • Help Your Community

The symptoms of severe disease (also called neuroinvasive disease, such as West Nile encephalitis or meningitis or West Nile poliomyelitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that approximately 1 in 150 persons infected with the West Nile virus will develop a more severe form of disease. Serious illness can occur in people of any age, however people over age 50 and some immunocompromised persons (for example, transplant patients) are at the highest risk for getting severely ill when infected with WNV.

Most people (about 4 out of 5) who are infected with West Nile virus will not develop any type of illness (an asymptomatic infection), however you cannot know ahead of time if you'll get sick or not when infected.

Q. What is the incubation period in humans (i.e., time from infection to onset of disease symptoms) for West Nile disease? A. Usually 2 to 15 days.

Q. How long do symptoms last? A. Symptoms of West Nile fever will generally last a few days, although even some healthy people report having the illness last for several weeks. The symptoms of severe disease (encephalitis or meningitis) may last several weeks, although neurological effects may be permanent.

Q. What is meant by West Nile encephalitis, West Nile meningitis, West Nile poliomyelitis, “neuroinvasive disease” and West Nile fever? A. The most severe type of disease due to a person being infected with West Nile virus is sometimes called “neuroinvasive disease,” because it affects a person's nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis, West Nile meningoencephalitis and West Nile poliomyelitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, meningoencephalitis refers to inflammation of the brain and the membrane surrounding it, and poliomyelitis refers to an inflammation of the spinal cord.



West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks.

Q. If I have West Nile Fever, can it turn into West Nile encephalitis? A. When someone is infected with West Nile virus (WNV) they will typically have one of three outcomes: No symptoms (most likely), West Nile fever (WNF in about 20% of people) or severe West Nile disease, such as meningitis or encephalitis (less than 1% of those who get infected). If you develop a high fever with severe headache, consult your health care provider.

West Nile fever is characterized by symptoms such as fever, body aches, headache and sometimes swollen lymph glands and rash. West Nile fever generally lasts only a few days, though in some cases symptoms have been reported to last longer, even up to several weeks. West Nile fever does not appear to cause any permanent health effects. There is no specific treatment for WNV infection. People with West Nile fever recover on their own, though symptoms can be relieved through various treatments (such as medication for headache and body aches, etc.).

Some people may develop a brief, WNF-like illness (early symptoms) before they develop more severe disease, though the percentage of patients in whom this occurs is not known.

Occasionally, an infected person may develop more severe disease such as “West Nile encephalitis,” “West Nile meningitis” or “West Nile meningoencephalitis.” Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. Although there is no treatment for WNV infection itself, the person with severe disease often needs to be hospitalized. Care may involve nursing IV fluids, respiratory support, and prevention of secondary infections.



West Nile Virus Poliomyelitis

Q. What is the “acute flaccid paralysis” that sometimes occurs with WNV infection? A. In addition to West Nile fever, meningitis, or encephalitis, some people who become infected with WNV can develop “acute flaccid paralysis”—a sudden onset of weakness in the limbs and/or breathing muscles. In most persons, acute flaccid paralysis is due to the development of West Nile poliomyelitis—an inflammation of the spinal cord that causes a syndrome similar to that caused by the poliovirus. West Nile poliomyelitis was first widely recognized in the United States in 2002. Persons with West Nile poliomyelitis may develop sudden or rapidly progressing weakness. The weakness tends to affect one side of the body more than the other, and may involve only one limb. The weakness is generally not associated with any numbness or loss of sensation, but may be associated with severe pain. In very severe cases, the nerves going to the muscles that control breathing may be affected, resulting in rapid onset of respiratory failure. It is important to recognize that this weakness may occur in the absence of meningitis, encephalitis, or even fever or headache—there may be few other clues that the weakness is due to WNV infection.

Q. How often does West Nile poliomyelitis occur? A. We don’t know for sure how often West Nile poliomyelitis occurs, but it does occur less frequently than meningitis or encephalitis. Scientists are continuing to monitor persons with West Nile poliomyelitis to get a better understanding of how often, and in whom, it occurs.

Q. Are there other types of weakness or “acute flaccid paralysis” caused by WNV infection? A. The vast majority of persons with WNV “acute flaccid paralysis” suffer from West Nile poliomyelitis (an inflammation of the spinal cord). Some persons with WNV infection may instead develop an illness similar to Guillain-Barré syndrome, which is a disease of the peripheral nerves and not the spinal cord. Weakness of the facial muscles may also develop in persons with WNV infection. While many persons with WNV infection experience fatigue and feel weak all over, this is not the same as “acute flaccid paralysis”.

Q. Who tends to be affected by West Nile poliomyelitis? A. People of any age can be affected by West Nile poliomyelitis. While persons over the age of 65 are at highest risk for all forms of WNV neuroinvasive disease, including poliomyelitis, persons of younger age groups (e.g., in their 30’s and 40’s) can also develop West Nile poliomyelitis. West Nile poliomyelitis may affect people who are otherwise healthy and without prior medical conditions.

Q. What is the likelihood that people who experience weakness due to West Nile poliomyelitis will recover? A. It is not yet clear the extent to which people who develop weakness due to West Nile poliomyelitis will recover. Some people do recover completely, others recover partially, and there are still others who have not shown significant recovery in over one year. Researchers continue to monitor patients who have been affected in order to better understand the long-term outcome of West Nile poliomyelitis and to determine whether there are any treatments that are beneficial.



Prevention Q. What can I do to reduce my risk of becoming infected with West Nile virus?

A. Here are preventive measures that you and your family can take:

Protect yourself from mosquito bites:

• Apply insect repellent to exposed skin. Generally, the the more active ingredient a repellent contains the longer it can protect you from mosquito bites. A higher percentage of active ingredient in a repellent does not mean that your protection is better—just that it will last longer. Click here for more on insect repellent active ingredients. Choose a repellent that provides protection for the amount of time that you will be outdoors.

o Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children.

o Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer's DIRECTIONS FOR USE, as printed on the product.

o For detailed information about using repellents, see the Insect Repellent Use and Safety questions.

• Spray clothing with repellents containing permethrin or another EPA-registered repellent since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. Do not apply repellent to skin under your clothing.

• When weather permits, wear long-sleeved shirts and long pants whenever you are outdoors.

• Place mosquito netting over infant carriers when you are outdoors with infants.

• Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times.

• Install or repair window and door screens so that mosquitoes cannot get indoors.

Help reduce the number of mosquitoes in areas outdoors where you work or play, by draining sources of standing water. In this way, you reduce the number of places mosquitoes can lay their eggs and breed.

• At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.

• Check for clogged rain gutters and clean them out. • Remove discarded tires, and other items that could collect water. • Be sure to check for containers or trash in places that may be hard to see,

such as under bushes or under your home.

Note: Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.







Look! Kids can learn how to protect themselves from mosquito bites on "The Buzz-z-z-z on West Nile Virus" (on BAM!, the CDC site for kids).

Q. What can be done to prevent outbreaks of West Nile virus? A. Prevention and control of West Nile virus and other arboviral diseases is most effectively accomplished through integrated vector management programs. These programs should include surveillance for West Nile virus activity in mosquito vectors, birds, horses, other animals, and humans, and implementation of appropriate mosquito control measures to reduce mosquito populations when necessary. Additionally, when virus activity is detected in an area, residents should be alerted and advised to increase measures to reduce contact with mosquitoes. Details about effective prevention and control of West Nile virus can be found in CDC's Guidelines for Surveillance, Prevention, and Control (286 KB, 111 pages).

Q. Is there a vaccine against West Nile encephalitis? A. No, but several groups are working towards developing a vaccine.

Q. Where can I get information about the use of pesticide sprays that are being used for mosquito control? A. The federal agency responsible for pesticide evaluation is the Environmental Protection Agency (EPA). See the EPA Web site for detailed answers to the questions about pesticides used for mosquito control.


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Insect Repellent Use and Safety

New for 2005

Updated information on insect repellents

Quick Links: General Active Ingredients Proper Use Children Sunscreen More Information

General Questions Q. Why should I use insect repellent? A. Insect repellents can help reduce exposure to mosquito bites that may carry viruses such as West Nile virus that can cause serious illness and even death. Using insect repellent allows you to continue to play and work outdoors with a reduced risk of mosquito bites.

Q. When should I use mosquito repellent? A. Apply repellent when you are going to be outdoors. Even if you don’t notice mosquitoes there is a good chance that they are around. Many of the mosquitoes that carry West Nile virus bite between dusk and dawn. If you are outdoors around these times of the day, it is especially important to apply repellent. In many parts of the country, there are mosquitoes that also bite during the day, and some of these mosquitoes have also been found to carry West Nile virus.

Q. How often should repellent be reapplied? A. In general you should re-apply repellent if you are being bitten by mosquitoes. Always follow the directions on the product you are using. Sweating, perspiration or getting wet may mean that you need to re-apply repellent more frequently.

Repellents containing a higher concentration (higher percentage) of active ingredient typically provide longer-lasting protection.

Q. How does mosquito repellent work? A. Female mosquitoes bite people and animals because they need the protein found in blood to help develop their eggs. Mosquitoes are attracted to people by skin odors and carbon dioxide from breath. The active ingredients in repellents make the person unattractive for feeding. Repellents do not kill mosquitoes. Repellents are effective only at short distances from the treated surface, so you may still see mosquitoes flying nearby.

Active Ingredients (Types of Insect Repellent)

Q. Which mosquito repellents work best? A. CDC recommends using products that have been shown to work in scientific trials and that contain active ingredients which have been registered with the US Environmental Protection Agency (EPA) for use as insect repellents on skin or clothing. When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that




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EPA does not expect a product, when used according to the instructions on the label, to cause unreasonable adverse effects to human health or the environment. Of the active ingredients registered with the EPA, CDC believes that two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature (See Publications page.). Products containing these active ingredients typically provide longer-lasting protection than others:

• DEET (N,N-diethyl-m-toluamide) • Picaridin (KBR 3023)

Oil of lemon eucalyptus [active ingredient: p-menthane 3,8-diol (PMD)], a plant- based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.

Q. How does the percentage of active ingredient in a product relate to the amount of protection it gives? A. Typically, the more active ingredient a product contains the longer it provides protection from mosquito bites. The concentration of different active ingredients cannot be directly compared (that is, 10% concentration of one product doesn’t mean it works exactly the same as 10% concentration of another product.)

DEET is an effective active ingredient found in many repellent products and in a variety of formulations. Based on a 2002 study (Fradin and Day, 2002. See Publications page.):

• A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites. • A product containing 20% DEET provided almost 4 hours of protection • A product with 6.65% DEET provided almost 2 hours of protection • Products with 4.75% DEET were both able to provide roughly 1 and a half hour of protection.

These examples represent results from only one study and are only included to provide a general idea of how such products may work. Actual protection will vary widely based on conditions such as temperature, perspiration, and water exposure.

Choose a repellent that provides protection for the amount of time that you will be outdoors. A product with a higher percentage of active ingredient is a good choice if you will be outdoors for several hours while a product with a lower concentration can be used if time outdoors will be limited. Simply re-apply repellent (following label instructions) if you are outdoors for a longer time than expected and start to be bitten by mosquitoes.

Q. Why does CDC recommend certain types of insect repellent? A. CDC recommends products containing active ingredients which have been registered with US Environmental Protection Agency (EPA) for use as insect repellents on skin or clothing. All of the EPA-registered active ingredients have demonstrated repellency however


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some provide more longerlasting protection than others. Additional research reviewed by CDC suggests that repellents containing DEET (N,N-diethyl-m-toluamide) or picaridin (KBR 3023) typically provide longer-lasting protection than the other products and oil of lemon eucalyptus (p-menthane-3,8-diol) provides longer lasting protection than other plant-based repellents. Permethrin is another long-lasting repellent that is intended for application to clothing and gear, but not directly to skin. In general, the more active ingredient (higher concentration) a repellent contains, the longer time it protects against mosquito bites.

People who are concerned about using repellents may wish to consult their health care provider for advice. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or npic.orst.edu

Q. How can you know which active ingredient a product contains? A. Check the product label if you have questions-–repellents must specify their active ingredients. In some cases you will note the chemical name in addition to/instead of the “common” name: • DEET is N,N-diethyl-m-toluamide • Picaridin is KBR 3023, sometimes known as “Bayrepel” outside the US • The active ingredient in oil of lemon eucalyptus is p-menthane 3,8-diol (PMD) Q. What is permethrin? A. Certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin.

Q. Where can I find these repellents? A. Most of these repellents are sold at multiple retail, discount and drug stores. A wider selection may be available at “outdoor” stores or in hunting and camping sections. At this time picaridin is not yet registered with the state pesticide programs in NY and CA, and thus is not available in those areas.

Q. Where can I find more information about picaridin? A. An technical fact sheet covering picaridin is available from EPA (http://www.epa.gov/opprd001/factsheets/picaridin.pdf)

Using Repellents Properly

Q. What are some general considerations to remember when using insect repellents? A. Always follow the recommendations appearing on the product label. • Use enough repellent to cover exposed skin or clothing. Don't apply repellent to skin that is under clothing. Heavy application is not necessary to achieve protection. • Do not apply repellent to cuts, wounds, or irritated skin. • After returning indoors, wash treated skin with soap and water. (This may vary



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depending on the product. Check the label.) • Do not spray aerosol or pump products in enclosed areas. • Do not spray aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.

Q. What are some reactions to be aware of when using insect repellents? A. Use of repellents products may cause skin reactions in rare cases. Most products also note that eye irritation can occur if product gets in the eye. If you suspect a reaction to a product, discontinue use, wash the treated skin, and call a poison control center. If product gets in the eyes flush with water and consult health care provider or poison control center. If you go to a doctor, take the product with you.

There is a national number to reach a Poison Control Center near you: 1-800-222-1222.

Children

Q. Can insect repellents be used on children? A. Repellent products must state any age restriction. If there is none, EPA has not required a restriction on the use of the product.

According to the label, oil of lemon eucalyptus products should NOT be used on CHILDREN UNDER 3 YEARS.

In addition to EPA’s decisions about use of products on children, many consumers also look to the opinion of the American Academy of Pediatrics (AAP). The AAP does have an opinion on the use of DEET in children (see below). AAP has not yet issued specific recommendations or opinion concerning the use of picaridin or oil of lemon eucalyptus for children. CDC will post a link to such information from the Academy when/if it becomes available. Since it is the most widely available repellent, many people ask about the use of products containing DEET on children. No definitive studies exist in the scientific literature about what concentration of DEET is safe for children. No serious illness has been linked to the use of DEET in children when used according to manufacturer’s recommendations.

The American Academy of Pediatrics (AAP) Committee on Environmental Health has updated their recommendation for use of DEET products on children in 2003, citing: "Insect repellents containing DEET (N,N-diethyl-m-toluamide, also known as N,N-diethyl-3-methylbenzamide) with a concentration of 10% appear to be as safe as products with a concentration of 30% when used according to the directions on the product labels." AAP recommends that repellents with DEET should not be used on infants less than 2 months old.

Parents should choose the type and concentration of repellent to be used by taking into account the amount of time that a child will be outdoors, exposure to mosquitoes, and the risk of mosquito-transmitted disease in the area.

If you are concerned about using repellent products on children you may wish to consult a health care provider for advice or contact the National Pesticide


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Information Center (NPIC) through their toll-free number, 1-800-858-7378 or npic.orst.edu

Q. What guidelines are available for using a repellent on children? A. Always follow the recommendations appearing on the product label when using repellent: • When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid children's eyes and mouth and use it sparingly around their ears. • Do not apply repellent to children's hands. (Children may tend to put their hands in their mouths.) • Do not allow young children to apply insect repellent to themselves; have an adult do it for them. • Keep repellents out of reach of children. • Do not apply repellent under clothing. If repellent is applied to clothing, wash treated clothing before wearing again. (May vary by product, check label for specific instructions.)

Q. How else can I protect children from mosquito bites? A. Using repellents on the skin is not the only way to avoid mosquito bites. Children (and adults) can wear clothing with long pants and long sleeves while outdoors. DEET or other repellents such as permethrin can also be applied to clothing (but is not registered for use on skin), as mosquitoes may bite through thin fabric.

Mosquito netting can be used over infant carriers.

Finally, it may be possible to reduce the number of mosquitoes in the area by getting rid of containers with standing water that provide breeding places for mosquitoes.

Q. Can insect repellents be used by pregnant or nursing women? A. Other than the routine precautions noted earlier, EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women. Consult your health care provider if you have questions.

Insect Repellents containing DEET and Sunscreen

Q. Can I use an insect repellent and a product containing sunscreen at the same time? What are the recomendations for combination sunscreen/insect repellent products ? A. Yes. People can, and should, use both a sunscreen and an insect repellent when they are outdoors. Follow the instructions on the package for proper application of each product. In general, the recommendation is to apply sunscreen first, followed by repellent.

It is recommended NOT to use a single product that combines insect repellent containing DEET and sunscreen, because the instructions for use of insect repellents and use of sunscreen are different. In most situations, insect repellent does not need to be reapplied as frequently as sunscreen. While no recommendations are available at this time regarding products that combine other active ingredients and sunscreen, it is important to always follow the label on whatever product you are using.




To protect from sun exposure and insect bites, you can also wear long sleeves and long pants. You can also apply insect repellent to your clothing, rather than directly to your skin.

More Information

Q. Where can I get more information about repellents? A. For more information about using repellents, please consult the Environmental Protection Agency (EPA) Web site or consult the National Pesticide Information Center (NPIC), which is cooperatively sponsored by Oregon State University and the U.S. EPA. NPIC can be reached at: npic.orst.edu or 1-800-858-7378.

West Nile virus vaccine

Q. Is there a vaccine available to protect humans from West Nile virus? A. No. Currently there is no WNV vaccine available for humans. Many scientists are working on this issue, and there is hope that a vaccine will become available in the next few years.

Q. Should people take the West Nile virus vaccine that is licensed for use in horses? A. No. This vaccine has not been studied in humans and could be harmful. The effectiveness of this vaccine in preventing West Nile virus infections in horses has yet to be fully evaluated, and its effectiveness in humans is completely unknown. Veterinary vaccines are not manufactured with the same rigorous quality and purity standards required of human vaccines, nor are they required to undergo the extensive field testing required of human vaccines before they are licensed. For these reasons, veterinary vaccines and other veterinary drugs should never be used in humans.


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Testing and Treating West Nile Virus in Humans UPDATED!

Questions about Commercial Laboratories NEW!

Q. I think I have symptoms of West Nile virus. What should I do? A. Contact your health care provider if you have concerns about your health. If you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches, you should see your doctor immediately.

Q. How do health care providers test for West Nile virus? A. Your physician will first take a medical history to assess your risk for West Nile virus. People who live in or traveled to areas where West Nile virus activity has been identified are at risk of getting West Nile encephalitis; persons older than 50 years of age have the highest risk of severe disease. If you are determined to be at high risk and have symptoms of West Nile encephalitis, your provider will draw a blood sample and send it to a commercial or public health laboratory for confirmation.

Q. How are human cases of WNV diagnosed? A. West Nile virus (WNV) infection can be suspected in a person based on clinical symptoms and patient history. Laboratory testing is required for a confirmed diagnosis.

The most commonly used WNV laboratory test measures antibodies that are produced very early in the infected person. These antibodies, called IgM antibodies, can be measured in blood or cerebrospinal fluid (CSF), which is the fluid surrounding the brain and spinal cord. This blood test may not be positive when symptoms first occur; however, the test is positive in most infected people within 8 days of onset of symptoms.

A test for WNV IgM-antibody is used by CDC, state and local public health labs and increasingly at private laboratories. When testing is conducted at private laboratories, the health department or CDC will often confirm results in their own laboratories before officially reporting WNV cases.

In some instances, health departments may conduct or request additional testing from CDC before officially reporting a case to CDC's ArboNET Surveillance System. The state or CDC reference laboratory may repeat the initial IgM-antibody testing.

A state may also perform or ask CDC to perform an additional, different test on a specimen. This latter test (plaque reduction neutralization test [PRNT]) is usually performed when:

• the state finds its initial case(s) of human WNV illness, • IgM results are not definitive due to equivocal laboratory testing results or

insufficient specimens, • the patient might have been exposed to other closely related viruses (like St.

Louis encephalitis virus) which may result in a "false" positive laboratory test for WNV.



These additional tests require growth of the virus and may take a week or longer (plus shipping time) to conduct. The results from the PRNT are often needed before CDC considers a human WNV infection confirmed.

Q. How does CDC decide when to report a case of WNV? A. CDC reports a case of WNV once a state officially reports and verifies that case to CDC.

The timing of the official report to CDC, relative to onset of symptoms in a person, is variable and depends on when an individual first seeks medical care and the extent of the laboratory testing, as described above, that the state determines is necessary before reporting.

At any given time, in addition to the official case count reported by CDC, there may be additional suspect cases under investigation or in various stages of testing, including supplemental or confirmatory laboratory testing.

Q. How many of the human WNV cases are being confirmed by the CDC laboratories? A. When WNV was first found in the United States in 1999, the CDC reference laboratory confirmed all human cases of WNV. Through a comprehensive, CDC-sponsored laboratory training program, most states are now able to perform the initial blood tests to identify IgM-antibody in the blood or CSF of suspect human WNV infections, and many state laboratories are also able to perform the more involved PRNT. The CDC reference lab is called upon for confirmatory testing by fewer and fewer states; although the increased activity of WNV still requires that many tests be performed at the CDC reference laboratory.

Q. How is West Nile encephalitis treated? A. There is no specific treatment for West Nile virus infection. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Questions about Commercial Laboratories New!

Q.What role do commercial laboratories play in diagnosing people with West Nile virus infection?

A.When a person goes to see a health care provider, and has symptoms of a West Nile illness a specimen may be sent to a commercial laboratory to determine if the person has been infected by West Nile virus. The tests used in commercial labs check for antibodies to the virus (the body’s response to infection). The results of the test will be sent to the doctor and the state health department will be informed if the results are positive. There is no specific treatment available for West Nile virus infection, so the diagnosis will not necessarily change the way the person is being



treated but it will let the doctor know that he/she does not have to investigate another cause of illness, and it will help the health department know where the virus is active in order to focus prevention measures.

The state health department may choose to accept the positive results from the commercial lab, or they may choose to test the sample again in the state health department laboratory for confirmation of the infection. The state health department will report the case to CDC.

Q.How accurate are the tests used in commercial labs?

A.The tests used in commercial labs are modeled on the tests created by CDC and used at CDC and in state public health laboratories. This is the first year that many of these tests have been widely used in commercial labs, and laboratories are learning more about the specific measurements used in each test. Often, a second test will be done to confirm the infection. State health departments, the FDA (which licenses and regulates medical tools such as these tests), the association of Public Health Laboratories and CDC are all engaged in monitoring new commercial tests, and are committed to working with industry to make these tests as accurate and useful as possible.

Q.If a test is a “false positive” what does that mean?

A.A “false positive” occurs when an initial tests indicates that a person does have a West Nile infection, but a later, more specific tests indicates that the person does not actually have the infection. While it is important to health department and CDC to get an accurate idea of where people are being infected in order to focus prevention and control efforts, the result does not have a great impact on the individual person. There is no specific treatment that the person would receive due to West Nile virus infection. The person may want to work with their physician to see if another cause of the illness needs to be identified.

West Nile Virus, Pregnancy and Breast-feeding Q. What risk does WNV illness during pregnancy present to a fetus? A. Based on the limited number of cases studied so far, it is not yet possible to



determine what percentage of WNV infections during pregnancy result in infection of the fetus or medical problems in newborns.

In 2002, one case of transplacental (mother-to-child) transmission of WNV was reported to CDC. In this case, the infant was born with WNV infection and severe medical problems. It is unclear, however, whether WNV infection caused these problems or whether they were due to other causes (see MMWR Dec 20, 2002).

After the report of this case, CDC and state and local health departments formed a registry to follow birth outcomes among women with WNV illness in pregnancy. Three additional pregnancies in which the expectant mother became infected with WNV were detected and evaluated in 2002; none of these 3 resulted in fetal infection. In one additional case it remains unclear whether the fetus was infected; appropriate testing was not done. In 2003, the registry identified 74 women who acquired WNV illness while pregnant. Preliminary findings regarding outcomes of these pregnancies were first presented at the Fifth Annual National West Nile Virus Conference in Denver CO on February 2, 2004. As of May 10, 2004, 62 of these women had delivered live infants, 2 had had elective abortions, 5 miscarried in the first trimester and 5 had not yet delivered.

In 2004, CDC is continuing to gather clinical and laboratory information on outcomes of pregnancies of women with WNV illness during pregnancy. Pregnant women who think they may have become infected with WNV should contact their private health care providers. Clinicians who are aware of WNV infections of pregnant women are encouraged to report such cases by calling their state or local health departments, or by contacting CDC, telephone 970-221-6400. For more information see the section on Clinical Guidance. Because of ongoing concerns that mother-to-child WNV transmission can occur with possible adverse health effects, pregnant women should take precautions to reduce their risk for WNV and other mosquito-borne infections by avoiding mosquitoes, using protective clothing, and using repellents containing DEET. Repellents with DEET are safe for pregnant women, and there are other options as well such as a soybean oil based repellent that provides good, though quite limited, protection, as judged by a study published in the new England Journal of Medicine. (See Using Repellent Safely.)

Pregnant women who become ill should see their health care provider, and those who have an illness consistent with acute WNV infection should undergo appropriate diagnostic testing.

Additional clinical information on intrauterine WNV can be found in these recent publications:

• Hayes EB and O'Leary DR. West Nile virus infection: a pediatric perspective. Pediatrics. 5 May 2004; 113(5): 1375-1381.

• Alpert SG, Fergerson J, Noel LP. Intrauterine West Nile virus: ocular and systemic findings. Am J Ophthalmol. 2003 Oct;136(4):733-5.

• Chapa et al. West Nile Virus Encephalitis During Pregnancy. Obstetrics and Gynocology. 2003 Aug; 102(2):229-231.



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Q. Where can I get more detailed clinical information about WNV in pregnancy? A. More information on issues that may be helpful to clinicians working with WNV can be found on the Clinical Guidance page.

Q. Are infants at higher risk than other groups for illness with West Nile virus? A. No. West Nile virus illnesses in children younger than 1 year old are infrequent. During 1999-2001, no cases in children younger than one year of age were reported to CDC. In 2002, 2,500 total West Nile Virus disease cases were reported to CDC, and only six occurred in children less than one year of age. The number of children infected with WNV during 2003 will be updated when data are finalized.

Breastfeeding

Q. Can West Nile virus be transmitted through breast milk? A. Based on a 2002 case in Michigan, it appears that West Nile virus can be transmitted through breast milk. A new mother in Michigan contracted West Nile virus from a blood transfusion shortly after giving birth. Laboratory analysis showed evidence of West Nile virus in her breast milk. She breastfed her infant, and three weeks later, her baby's blood tested positive for West Nile virus. Because of the infant's minimal outdoor exposure, it is unlikely that infection was acquired from a mosquito. The infant was most likely infected through breast milk. The child is healthy, and does not have symptoms of West Nile virus infection.

Q. If I am pregnant or breast-feeding, should I use insect repellent containing DEET? A. Yes. Insect repellents help people reduce their exposure to mosquito bites that may carry potentially serious viruses such as West Nile virus, and allow them to continue to play and work outdoors. There are no reported adverse events following use of repellents containing DEET in pregnant or breast-feeding women. Click here for more information about using repellents safely.

Q. Should I continue breast-feeding if I am symptomatic for West Nile virus? A. Because the health benefits of breast-feeding are well established, and the risk for West Nile virus transmission through breast-feeding is unknown, the new findings do not suggest a change in breast-feeding recommendations.

Lactating women who are ill or who are having difficulty breast-feeding for any reason should, as always,consult their physicians.

Q. Should I continue breast-feeding if I live in an area of WNV transmission? A. Yes. Because the health benefits of breast-feeding are well established, and the risk for West Nile virus transmission through breast-feeding is unknown, the new findings do not suggest a change in breast-feeding recommendations.

Q. If I am breast-feeding, should I be tested for West Nile virus? A. No. There is no need to be tested just because you are breast-feeding.


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Blood Transfusion, Organ Donation and Blood Donation Screening Information UPDATED!

Guidance related to donated organs, and the use of screening and diagnostic tests for West Nile virus was issued January 9, 2004 and is posted on the website of the Organ Procurement and Transplantation Network.

NEW!Transfusion Complications PDF (70KB/5 pages), West Nile Virus blood transfusion-related infection despite nucleic acid testing, December 2004.

The most recent information on West Nile Virus Screening of Blood Donations and Transfusion-Associated Transmission is found in this update of the MMWR Dispatch April 9, 2004.

Also, Detection of West Nile Virus in Blood Donations---United States, 2003 is found in the MMWR Dispatch September 18, 2003.

For General Information about Screening of Blood Donations for WNV, click here.

Update on Detection of WNV in Blood Donations -- from MMWR, September 18, 2003 Q. How many blood donations have been screening for WNV in 2003? A. According to numbers reported to CDC by blood collection agencies, approximately 2.5 million blood donations have been screened for WNV since approximately July 2003.

Q. How many potentially infectious blood donations have been identified? A. State health departments have reported 489 WNV-viremic donors (e.g. donors who were infected with West Nile virus without any signs of illness at the time they donated blood) to CDC's ArboNet surveillance system as of September 16, 2003. Information from blood collection agencies indicates that 601 viremic donations have been identified, with additional testing underway for another 209 donations. Since each blood donation is separated into component parts that may then be given to different recipients, the identification and removal of these donations from the blood system represents more than one thousand potential recipient infections have been prevented.

Q. Have any cases of blood transfusion-associated WNV infection occurred in 2003? A. Yes, two cases of blood transfusion-associated WNV infection have been detected in the US in 2003, 1 in Texas and 1 in Nebraska. Both persons were receiving care -- including blood transfusions -- for other serious health conditions, they developed encephalitis as a result of WNV infection and are recovering as of 9/16/2003. These cases indicate that the risk of transfusion-related WNV transmission has not been completely eliminated.


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In both 2003 cases of transfusion-associated transmission of WNV, the WNV-contaminated blood donations that infected these persons had screened negative during initial minipool testing. When the donations comprising the minipools were tested individually during a retrospective examination it was found that these two donations contained very low levels of WNV.

Q. What do these cases of transfusion-associated WNV infection mean for the WNV testing of the blood supply? A. These findings suggest a need to develop more sensitive screening tests for use in minipool testing, or that individual donation testing (instead of minipool testing) might be considered in areas experiencing a high number of WNV infections, depending on the testing capacity of the Blood Collection Agency. Currently it is not feasible to test individually all blood donations made in the United States, however individual donation testing is being put into place at selected blood banks serving Kansas, Nebraska, North Dakota Oklahoma and South Dakota. It is also important that health care providers continue to investigate WNV illness in people who have received blood transfusions and to report suspected transfusion-associated cases to state health authorities.

Q. What has been achieved through the efforts to screen the blood supply? Has the program been a success? A. The implementation of donor screening for WNV in 2003 has reduced the risk of transfusion-associated WNV infection substantially by removing hundreds of units of potentially infectious blood products donated by asymptomatic donors. CDC will continue to work with FDA, blood collection agencies and industry to identify the best approaches to use in the future to ensure the safety of the blood supply.

General Information on Screening of Blood Donations for WNV

Q. What is being done to reduce the risk of transfusion-related West Nile virus transmission in 2003? A. In 2003, all blood banks are using blood screening tests for West Nile virus. In addition, blood banks will not take donations from people who have fever and headache in the week before they donate blood. The screening tests is in place at all of the nation's blood banks. State and local public health departments will report cases of West Nile virus infection in patients who have received blood transfusions in the 4 weeks before they got sick to the blood collection agency that collected the donation and to CDC from through ArboNET, the national database where information about cases of West Nile virus is kept. In addition, cases of West Nile virus infection in people who donated blood in the 2 weeks preceding illness onset should also be reported to CDC and blood collection agencies where the sick person donated blood. The blood collection agency will destroy potentially infectious units of blood.

The new screening methods will allow blood banks to destroy potentially infectious blood before it is given to anyone. To reduce the number of donations from



potentially infected people, blood banks will refuse to accept blood from people with recent fever and headaches.

In addition, public health departments and blood banks will cooperate to identify and destroy blood products (if necessary) from donors who develop a West Nile viral illness after they give blood. If someone becomes ill after a transfusion, blood banks will destroy the blood products taken from the donor of the transfused blood. Prompt reporting of these cases will help facilitate withdrawal of potentially infected blood components.

CDC, the Food and Drug Administration (FDA), and the Health Resources and Services Administration (HRSA), blood collection agencies and state and local health departments will continue to investigate West Nile virus infections in people who receive blood transfusions and transplanted organs to make sure these new screening methods are working.

For more information on current efforts by the FDA see: http://www.fda.gov/cber/gdlns/wnvguid.htm

Q. Should people avoid donating blood? A. No. There is no risk of West Nile virus infection for people who give blood. Blood saves lives and is always needed, especially during the summer months. Because donating blood is safe, we encourage blood donation now and in the future. We also encourage all donors to truthfully answer the questions asked by the blood bank to make sure you are fit to donate on a given day.

Q. Should people avoid getting blood transfusions or organ transplants? A. Roughly 4.5 million people receive blood or blood products annually. The benefits of receiving needed transfusions or transplants outweigh the potential risk for West Nile virus infection. However, doctors and their patients who need blood transfusions or organ transplants should be aware of the risk for West Nile virus infection.

Q. How can blood banks avoid collecting blood from donors who may have West Nile virus? A. On May 5, 2003, FDA issued guidance for blood banks that describes methods to screen out potential blood donors who have symptoms that suggest West Nile viral illness (i.e., headache, fever) and to define blood product safety practices with regards to West Nile virus (http://www.fda.gov/cber/gdlns/wnvguid.htm).

Because most people who have West Nile virus infections do not have symptoms, it may be difficult to identify them. To avoid this problem, blood banks and their industry partners have developed tests to screen the blood for West Nile virus. As of July 14, 2003, every blood bank in the US is screening donated blood for WNV.

Q. If a person had a West Nile virus infection in the past, can they still donate blood? A. Yes. West Nile virus infections do not last very long. The virus is in the blood for a very short time. People fight the virus and usually get rid of it in a few days. When they get rid of the virus, they develop an antibody (a protein that helps fight infections). Developing an antibody means that you are fighting the infection. The


http://www.fda.gov/cber/gdlns/wnvguid.htm

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.fda.gov/cber/gdlns/wnvguid.htm


antibody will keep them from getting a West Nile virus infection again and will keep the virus out of their blood.

Potential blood donors with a medical diagnosis of West Nile viral illness that includes a compatible illness and laboratory results should not be allowed to donate for at least 28 days from the start of their symptoms OR until 14 days after they recover, whichever date is later. If there are no symptoms to suggest a West Nile virus illness, a positive West Nile virus antibody test result alone should not be grounds for refusing a blood donation.

Q. If I recently had a transfusion or transplant, should I be concerned about getting West Nile virus? A. You should be aware of the potential risk for West Nile virus infection and the need to monitor your health. If you have symptoms of West Nile virus or other concerns you should contact your physician. A large number of West Nile virus infections due to mosquito bites occurred among people in the United States during 2002. Some of these people also received blood transfusions and/or organ transplantations. If a patient who recently received a blood transfusion or organ transplantation develops an infection, that does not necessarily mean that the transfusion/transplantation was the source of infection.

Q. I have heard reports of donors with WNV infection being found at blood banks, but they don't show up on the maps CDC provides. Why? A. CDC maps include people with WNV illness who are reported to CDC by state health departments. Because people with fever and headache in the week before donation are not allowed to donate blood, the infections found by the blood banks are from donors without symptoms at the time of donation. As a result, they are not considered "cases." Occasionally, a donor may develop symptoms of WNV illness after donation. Then, the person would be counted as a case by the health department and reported to CDC.

It is important to know that screening tests used at blood collection centers are very new, and a much additional testing will be needed to confirm whether a blood donation is truly infected with WNV. Although the blood donation is removed from the blood supply as soon as the initial screening test shows that it could be infected, it may take several more weeks to confirm the infection.

Q. How can a person test positive for WNV infection at a blood bank, but not be considered a "case" by CDC? A. A WNV "case" is a person who has become ill and been confirmed to have WNV infection. This infection might be either West Nile Fever, a mild illness with fever, or West Nile encephalitis or meningitis, more severe illnesses. Blood donors who do not become ill and do not develop symptoms are counted in a separate category because they are not considered "cases."

For more information on human cases, disease surveillance, and a map of cases, go to http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm.

Q. What kind of test is used to test donated blood? A. During the 2002 WNV epidemic, the blood-banking industry, FDA, and CDC




worked together closely to identify WNV transmission to humans through blood transfusion and organ donation. These screening tests identify whether West Nile virus is present in the blood. The tests used to screen the blood supply were developed quickly because they were based on tests previously developed and used at CDC. The tests being used for the blood supply are experimental test and they are being carefully evaluated by all the agencies involved.

If the experimental test is positive, the blood from this donation is removed from the blood supply. To further evaluate these new tests, further testing is done. In some cases, the screening test result may be a "false positive" because the new test is still being adjusted, and blood banks are taking a cautious approach to avoid future WNV transmission by transfusion. For more information, consult the FDA WNV Web page at http://www.fda.gov/oc/opacom/hottopics/westnile.html.

These blood-screening tests are different than the tests that are used to diagnose WNV infections among ill people who are not donors. Among people who are not donors, we use tests that identify antibodies (proteins in the blood that help fight infection) that are produced by the body in response to a WNV infection.

Q. What happens to the blood collected from donors that test positive for WNV? A. As soon as a unit of blood is identified as possibly infected with WNV by initial screening, it is removed from the blood supply. If the confirmation process reveals that the unit is NOT actually infected, the remaining blood products may be used,

Q. Is there enough blood to meet the needs of hospitals? A. Although there is always an increased demand for blood products during summer months, only a relatively few units of blood will be removed from the blood supply even if a few uninfected products are removed because of "false positive" tests.

Blood donations usually decrease in summer. Despite the recently identified problems with receiving infectious blood, it is still safe to donate blood. CDC encourages people who can donate to consider making a donation during summer months to help ensure adequate blood supplies for all who need them. If you have symptoms consistent with possible WNV infection (such as fever and headache) you will be deferred from donating at that time but will be allowed to donate again when you feel better.

Q. If someone who is donating blood at the same time that I do tests positive for WNV, can I catch it from them? A. No. WNV is generally transmitted through the bite of an infected mosquito. You cannot get infected with WNV from contact with an infected person. For more information, see the Transmission page.

Q. If a blood bank does not use my blood because it tests positive for WNV, does this mean I'm going to get sick? A. Probably not. What this means is that you have WNV in your blood, so you have been recently bitten by an infected mosquito. Most infected people do not become ill at all and only a very small number develop West Nile fever or more serious disease. It is thought that you will have immunity from WNV for a long period after becoming infected, possibly for life. For more information, visit the Transmission page.


http://www.fda.gov/oc/opacom/hottopics/westnile.html




Q. Will the blood bank notify me if my blood tests positive for WNV? A. Blood banks will contact donors who may have a WNV infection. A subsequent blood sample will be requested in order to help confirm the infection. We thank you in advance for your cooperation in protecting the national blood supply, and helping to validate the tests that are being used.

Q. What do I need to do if my blood tests positive for WNV? A. If you learn from a blood bank that your blood was likely infected with WNV you may be requested to give another blood sample to help confirm the infection.

Most WNV infections do not cause any symptoms, and do not require any medical attention. There is nothing in particular that you need to do because of the infection. It is also likely that you have antibodies to prevent you from getting sick with WNV in the future. If you were infected with WNV, this does tell you that there is a risk of infection in your area, and it is important for the rest of your family to protect themselves.

Of course if you do feel ill you should consult your health care provider.

Q. Can I get tested for WNV at my doctor's office with the new blood test that blood banks are using? A. No. The tests being used at blood banks are new and not licensed by the FDA. These tests are being used only at blood banks. This new type of testing was necessary because WNV tests that look for antibodies (the proteins that are a response to infection) cannot detect the actual virus in blood from very recently infected individuals.

If your health care provider suspects you may have WNV illness he/she can send a sample of your blood to a private laboratory or to the state health department for testing.

Q. Are all U.S. blood banks testing the blood they collect for WNV? A. Yes. Most blood banks in the U.S. have been screening blood since July 1, 2003 and as of July 14, 2003, CDC was informed by the American Association of Blood Bankers that screening is going on in every U.S. civilian blood bank, including Alaska and Hawaii and Puerto Rico.

See Also –

• Transmission • Food and Drug Administration West Nile Virus Site



http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.fda.gov/oc/opacom/hottopics/westnile.html


Pesticides Used in Mosquito Control Q. What are "larvicides" and "adulticides"? A. Larvicides are products used to kill immature mosquitoes. They can be either biological (such as toxin from specific bacteria that is lethal to mosquito larvae but not to other organisms) or chemical products, such as insect growth regulators, surface films, or organophosphates. Larvicides are applied directly to water sources that hold mosquito eggs or larvae. When used well, larvicides can help to reduce the overall mosquito by limiting the number of new mosquitoes that are produced.

Adulticides are products used to kill adult mosquitoes. Adulticides can be applied from hand-held sprayers, truck-mounted sprayers or using airplanes. Adulticides, when used well, can have an immediate impact to reduce the number of adult mosquitoes in an area, with the goal of reducing the number of mosquitoes that can bite people and possibly transmit West Nile virus.

Both larvicides and adulticides are regulated by the US Environmental Protection Agency.

Q. What is CDC's position regarding the use of chemical mosquito control? A. Chemical control measures are one part of a comprehensive and integrated mosquito management program. An integrated program is the most effective way to prevent and control mosquito-borne disease. An integrated mosquito management program should include several components: (1) surveillance (monitoring levels of mosquito activity, and where virus transmission is occurring), (2) reduction of mosquito breeding sites, (3) community outreach and public education, and (4) the ability to use chemical and biological methods to control both mosquito larvae and adult mosquitoes.

Control measures, including the decision to use chemical adulticides (pesticides to kill adult mosquitoes) should be based on surveillance data and the risk of human disease. CDC's Revised Guidelines for Surveillance, Prevention, and Control of West Nile Virus in the US, 2003 [254 KB, 77 pp].)provides detailed guidance about the use of control measures, including a suggestions for a phased response and the actions that are possible at different levels of virus activity.

Q. Are pesticides harmful to people? A. Effect on human health is one of the primary factors considered in regulation of pesticides. Pesticides that can be used for mosquito control have been judged by the EPA not to pose an unreasonable risk to human health. People who are concerned about exposure to a pesticide, such as those with chemical sensitivity or breathing conditions such as asthma can reduce their potential for exposure by staying indoors during the application period (typically nighttime). A recently published study, (MMWR, July 11, 2003) examined illnesses in nine states associated with exposure to pesticides used to control mosquito populations from 1999-2002. This study found that "application of certain insecticides poses a low risk for acute, temporary health effects among person in areas that were sprayed and among workers handling and applying insecticides." This article can be viewed online.


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=%20http://www.epa.gov/pesticides%20


http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-guidelines-aug-2003.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-guidelines-aug-2003.pdf




For more information on pesticides and health, consult the US Environmental Protection Agency, which oversees the registration of these chemicals. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or online.

Q. What should I do if I think that I am having health problems because of pesticides used in my area? A. If you are experiencing health problems for any reason it is important to see your health care provider promptly. If you are experiencing severe health problems go immediately to an Emergency Room.

Q. How does pesticide spraying affect the environment? A. A great deal of research must be done before pesticides can be used in the environment. The best source for finding out about the pesticides used in your area, and their effect on specific types of wildlife, is with he US Environmental Protection Agency, which oversees the registration of these products. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or online.

Q. What training is required for workers who apply pesticides? A. Each state has mandated training and experience requirements that must be met before an individual can commercially apply pesticides. In New York state, for example, certified pesticide apprentices must be at least 16 years of age, have completed an 8-hour core training course on safety issues and the use of pesticides, and have at least 40 hours of pesticide use experience in the field under the direct supervision of a certified pesticide applicator. In addition, these applicators must follow the instructions and precautions that are printed on the pesticide label. All pesticide products are required to have a label which provides information, including instructions on how to apply the pesticide and precautions to be taken to prevent health and environmental effects. All labels are required to be approved by U.S. EPA.

Q. Where can I get information regarding the safety of specific pesticides? A. Questions concerning specific pesticides can be directed to the U.S. Environmental Protection Agency, as this agency has responsibility for registration of pesticides. Many issues are addressed on the EPA's Mosquito Control Web site.

The National Pesticide Information Center (NPIC) provides pesticide information and questions about the impact of pesticide use on human health. NPIC is cooperatively sponsored by Oregon State University and the U.S. Environmental Protection Agency. NPIC can be reached online or toll-free: 1-800-858-7378.

Q. How can I find out what type of pesticides are being used in my area? A. Your local mosquito control program or health department can give information about the type of products being used in an area. Mosquito control activities are most often handled at the local level, such as through county or city government. Check with your health department or in the "blue" (government) pages of the phone book for the contacts in your area.

Another resource to learn more about mosquito control is the American Mosquito Control Association.




http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=%20http://npic.orst.edu/.






http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.epa.gov/pesticides/factsheets/skeeters.htm%20

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http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.mosquito.org%20

http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.mosquito.org%20


West Nile Virus and Dogs and Cats NEW!! *A recent article (Austgen et al. Experimental Infection of Cats and Dogs with West Nile Virus, EID, Vol. 10, no.1 Jan 2004) in the journal Emerging Infectious Diseases discusses WNV infection in dogs and cats in detail.

Q. Can West Nile virus (WNV) cause illness in dogs or cats? A. A relatively small number of WNV infected dogs (<40) and only 1 WNV infected cat have been reported to CDC during 2003. Experimentally infected dogs* showed no symptoms after infection with WNV. Some infected cats exhibited mild, nonspecific symptoms during the first week after infection--for the most part only showing a slight fever and slight lethargy.

It is unlikely that most pet owners would notice any unusual symptoms or behavior in cats or dogs that become infected with WNV.

Q. How can my veterinarian treat my cat or dog if they are/may be infected with WNV? A. There is no specific treatment for WNV infection. Full recovery from the infection is likely. Treatment would be supportive (managing symptoms, if present) and consistent with standard veterinary practices for animals infected with a viral agent.

Q. Does my dog/cat becoming infected pose a risk to the health of my family or other animals? A. There is no documented evidence of dog or cat-to-person transmission of West Nile virus. The evidence suggests that dogs do not develop enough virus in their bloodstream to infect more mosquitoes. Cats develop slightly higher levels of virus in their bloodstream, but it is unclear if this would be enough to infect mosquitoes. It is very unlikely that cats would be important in furthering the spread of the virus. * If your animal becomes infected with WNV, this suggests that there are infected mosquitoes in your area. You should take measures to prevent mosquitoes from biting you (use repellent and wear protective clothing.) Veterinarians should take normal infection control precautions when caring for any animal (Including birds) suspected to have this or any viral infection.

Q. How do cats and dogs become infected with West Nile virus? A. Dogs and cats become infected when bitten by an infected mosquito. There is also evidence that cats can become infected with the virus after eating experimentally infected mice. *

Q. Can I become infected with WNV if a dog with the virus bites me? A. Preliminary studies have not been able to detect virus in the saliva of infected dogs. This suggests that dog bites pose a low risk, if any, of transmission of WNV from dogs to other animals or people.

Q. Is there a vaccine for cats or dogs? A. No.


http://www.cdc.gov/ncidod/eid/vol10no1/02-0616.htm



Q. Should a dog or cat infected with West Nile virus be destroyed? A. No. There is no reason to destroy an animal just because it has been infected with West Nile virus. Full recovery from the infection is likely. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Q. Can I use insect repellent on my pets? A. DEET-based repellents, which are recommended for humans, are not approved for veterinary use (largely because animals tend to ingest them by licking.) Talk with your veterinarian for advice about the appropriate product for use on your pet.

West Nile Virus and Horses Q. Has West Nile virus caused severe illness or death in horses? A. Yes, while data suggest that most horses infected with West Nile virus recover, results of investigations indicate that West Nile virus has caused deaths in horses in the United States.

Q. How do the horses become infected with West Nile virus? A. The same way humans become infected—by the bite of infectious mosquitoes. The virus is located in the mosquito's salivary glands. When mosquitoes bite or "feed" on the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.

Q. How does the virus cause severe illness or death in horses? A. Following transmission by an infected mosquito, West Nile virus multiplies in the horse's blood system, crosses the blood brain barrier, and infects the brain. The virus interferes with normal central nervous system functioning and causes inflammation of the brain.

Q. Can I get infected with West Nile virus by caring for an infected horse? A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of West Nile virus. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.

Q. Can a horse infected with West Nile virus infect horses in neighboring stalls? A. No. There is no documented evidence that West Nile virus is transmitted between horses. However, horses with suspected West Nile virus should be isolated from mosquito bites, if at all possible.

Q. My horse is vaccinated against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE). Will these vaccines protect my horse against West Nile virus infection?



A. No. EEE, WEE, and VEE belong to another family of viruses for which there is no cross-protection.

Q. Can I vaccinate my horse against West Nile virus infection? A. A West Nile virus vaccine for horses was recently approved, but its effectiveness is unknown.

Q. How long will a horse infected with West Nile virus be infectious? A. We do not know if an infected horse can be infectious (i.e., cause mosquitoes feeding on it to become infected). However, previously published data suggest that the virus is detectable in the blood for only a few days.

Q. What is the treatment for a horse infected with West Nile virus? Should it be destroyed? A. There is no reason to destroy a horse just because it has been infected with West Nile virus. Data suggest that most horses recover from the infection. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Q. Where can I get more information on horses and West Nile virus? A. Visit the USDA Web site Animal and Plant Health Inspection Service (APHIS).

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West Nile Virus and Squirrels

Q. Can squirrels infected with West Nile virus transmit the virus to humans? A. A small number of squirrels have tested positive for the West Nile virus. There is no evidence that people could become infected with the West Nile virus by being near an infected squirrel or in the yard with a dead one. However, the presence of an infected squirrel does mean that there could be infected mosquitoes nearby, and people should use protective clothing and repellent, and avoid maintaining mosquito-breeding sites on their property.


http://www.bt.cdc.gov/cdclinkdisclaimer.asp?a_gotolink=http://www.aphis.usda.gov/lpa/issues/wnv/wnv.html


West Nile Virus and Wild Game/Meat UPDATED!

NEW! Q. Is there a risk of getting infected with West Nile virus (WNV) if I eat turkey or another animal that has been infected with the virus? A. There is no evidence that people can become infected with WNV from eating infected meat. The small, theoretical risk of infection can be eliminated by proper handling and thorough cooking of meat before it is consumed. Several well-known and potentially serious food-borne illnesses can occur when turkey and other meats are improperly handled or undercooked. For more information on food safety, please see: http://www.cdc.gov/foodsafety/

Q. What is known about the risk of West Nile virus infection from dried, uncooked meat (jerky)? A. There are no published studies that directly address this question. Most studies indicate that while mammals can become infected with West Nile virus, they do not develop high concentrations of virus in their blood or tissues. Although it is unlikely that dried meat from mammals would have much virus present, and probable that gastrointestinal digestion would further limit the possibility of infectiousness, there is insufficient evidence to determine whether dried meat presents a risk of West Nile virus infection to humans or other animals. If you have questions about this topic it may be advisable to contact local wildlife authorities and/or health authorities to find out whether the area where the animal was harvested has West Nile virus activity, and whether animals of the species in question were affected.

Q. Are duck and other wild game hunters at risk for West Nile virus infection? A. Because of their outdoor exposure, game hunters may be at risk if they are bitten by mosquitoes in areas with West Nile virus activity. The extent to which West Nile virus may be present in wild game is unknown.

Q. What should wild game hunters do to protect against West Nile virus infection? A. Hunters should follow the usual precautions when handling wild animals. If they anticipate being exposed to mosquitoes, they should apply insect repellent to clothing and skin, according to label instructions, to prevent mosquito bites. Hunters should wear gloves when handling and cleaning animals to prevent blood exposure to bare hands and meat should be cooked thoroughly.

Q. Who should wild game hunters contact for information about the risk for West Nile virus infection in specific geographic areas? A. Hunters should check with their local area department of wildlife and naturalist resources, state epidemiologist at the state health department, or the US Geological Survey (USGS) National Wildlife Health Center, Madison, WI, 608-270-2400 for information on local area risk.


http://www.cdc.gov/foodsafety/


• West Nile Virus Activity --- United States, November 9--16, 2004 Morbidity and Mortality Weekly Report (MMWR)November 19, 2004 / 53(45);1071-1072

• West Nile Virus Activity --- United States, November 3--8, 2004 Morbidity and Mortality Weekly Report (MMWR)November 12, 2004 / 53(44);1050-1051

• West Nile Virus Activity --- United States, October 27--November 2, 2004 Morbidity and Mortality Weekly Report (MMWR)November 5, 2004 /53,(43);1022

• West Nile Virus Activity --- United States, October 20--26, 2004 Morbidity and Mortality Weekly Report (MMWR)October 29, 2004 / 53(42);996

• West Nile Virus Activity --- United States, October 13--19, 2004 Morbidity and Mortality Weekly Report (MMWR)October 22, 2004 / 53(41);971-972

• West Nile Virus Activity --- United States, October 6--12, 2004 Morbidity and Mortality Weekly Report (MMWR)October 15, 2004 / 53(40);950-951

• West Nile Virus Activity --- United States, September 29--October 5, 2004 Morbidity and Mortality Weekly Report (MMWR)October 8, 2004 / 53(39);922-923

• West Nile Virus Activity --- United States, September 22--28, 2004 Morbidity and Mortality Weekly Report (MMWR)October 1, 2004 / 53(38);900

• West Nile Virus Activity --- United States, September 15--21, 2004 Morbidity and Mortality Weekly Report (MMWR)September 24, 2004 / 53(37);875-876

• West Nile Virus Activity --- United States, September 8--14, 2004 Morbidity and Mortality Weekly Report (MMWR)September 17, 2004 / 53(36);850-851

• West Nile Virus Activity --- United States, September 1--7, 2004 Morbidity and Mortality Weekly Report (MMWR)September 10, 2004 /53(35);823-824

• West Nile Virus Activity --- United States, August 25--31, 2004 Morbidity and Mortality Weekly Report (MMWR)September 3, 2004 / 53(34);795-796

• West Nile Virus Activity --- United States, August 18--24, 2004 Morbidity and Mortality Weekly Report (MMWR) August 27, 2004 / 53(33);770-771



• West Nile Virus Activity --- United States, July 28--August 3, 2004 Morbidity and Mortality Weekly Report (MMWR) August 5, 2004 / 53(30);686-687

• West Nile Virus Activity --- United States, July 21--27, 2004 Morbidity and Mortality Weekly Report (MMWR) July 30, 2004 / 53(29);661-662






















• West Nile Virus Activity --- United States, July 14--20, 2004 Morbidity and Mortality Weekly Report (MMWR) July 23, 2004 / 53(28);638-639

• West Nile Virus Activity --- United States, July 7--13, 2004 Morbidity and Mortality Weekly Report (MMWR) July 16, 2004 / 53(27);615

• West Nile Virus Activity --- United States, June 30--July 6, 2004 Morbidity and Mortality Weekly Report (MMWR) July 9, 2004 / 53(26);586

• West Nile Virus Activity --- United States, June 23--29, 2004 Morbidity and Mortality Weekly Report (MMWR) July 2, 2004 / 53(25);563

• West Nile Virus Activity --- United States, June 16--22, 2004 Morbidity and Mortality Weekly Report (MMWR) June 25, 2004 / 53(24);535-536

• West Nile Virus Activity --- United States, June 9--15, 2004 Morbidity and Mortality Weekly Report (MMWR) June 18, 2004 / 53(23);511-512

• West Nile Virus Activity --- United States, June 2--8, 2004 Morbidity and Mortality Weekly Report (MMWR) June 11, 2004 / 53(22);484

MMWR Publications Archived 1999-2003

Emerging Infectious Disease Journal, by Date

• Alligators as West Nile Virus Amplifiers. Kaci Klenk et al. Emerging Infectious Diseases December 2004; 10(12). (Also available in PDF format [139 KB, 6 pp.])

• Differential Virulence of West Nile Strains for American Crows. Aaron C. Brault et al. Emerging Infectious Diseases December 2004; 10(12). (Also available in PDF format [224 KB, 8 pp.])

• Experimental Infection of Cats and Dogs with West Nile Virus. Austgen et al. Emerging Infectious Diseases Jan 2004; 10(1). [PDF forthcoming]

• Dead Bird Clusters as an Early Warning System for West Nile Virus Activity. Mostashari et al. Emerging Infectious Diseases June 2003; 9(6) (Also available in PDF format [299 KB, 6 pp.])

• Imported West Nile Virus Infection in Europe . Charles et al. Emerging Infectious Diseases June 2003; 9(6) (Also available in PDF format [152 KB, 1 pp.])

• Early-Season Avian Deaths from West Nile Virus as Warnings of Human Infection. Guptill et al.Emerging Infectious Diseases Apr 2003; 9(4) (Also available in PDF format [195 KB, 2 pp.])

• First Isolation of West Nile virus from a Patient with Encephalitis in the United States. Huang et al. Emerging Infectious Diseases Dec 2002; 8(12):1367-1371.(Also available in PDF format [491 KB, 5 pp].)

• Vector Competence of California Mosquitoes for West Nile virus. Goddard et al. Emerging Infectious Diseases Dec 2002; 8(12):1385 -1391. (Also available in PDF format [249 KB, 7 pp].)

• Efficacy of Killed Virus Vaccine, Live Attenuated Chimeric Virus Vaccine, and Passive Immunization for Prevention of West Nile virus Encephalitis in Hamster Model. Tesh et al. Emerging Infectious Diseases Dec 2002; 8(12):1392 -1397. (Also available in PDF format [325 KB, 6 pp].)









http://www.cdc.gov/ncidod/dvbid/westnile/publications_Archive.htm

http://www.cdc.gov/ncidod/EID/vol10no12/04-0264.htm

http://www.cdc.gov/ncidod/eid/vol10no12/pdfs/04-0486.pdf












http://www.cdc.gov/ncidod/EID/vol9no4/pdfs/02-0421.pdf













• Induction of Inflammation by West Nile virus Capsid through the Caspase-9 Apoptotic Pathway Yang et al. Emerging Infectious Diseases Dec 2002; 8(12):1379 - 1384. (Also available in PDF format [470 KB, 6 pp.].)

• West Nile virus Epidemic in Horses, Tuscany Region, Italy. Autorino et al. Emerging Infectious Diseases Dec 2002; 8(12):1372-1378. (Also available in PDF format [459 KB, 7pp].)

• Special West Nile Virus Edition of Emerging Infectious Diseases Journal. Aug 2001;7(4). (Also available in PDF format [3.08 MB, 161 pp].)

• Migratory Birds and Spread of West Nile Virus in the Western Hemisphere. Rappole JH, Derrickson SR, Hubálek Z. Emerging Infectious Diseases Jul-Aug 2000;6:319-328. (Also available in PDF format [148 KB, 10 pp].)

• West Nile Fever—a Reemerging Mosquito-Borne Viral Disease in Europe. Hubálek Z, Halouzka J. Emerging Infectious Diseases Sep-Oct 1999;5:643-650. (Also available in PDF format [107 KB, 8 pp].)

Guidelines

• Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention, and Control.

o 2003/3rd release(271 KB, 80 pages) o 2001/February(684 KB, 112 pages) o 1999/November(340 KB, 52 pages)

• Guidelines for Arbovirus Surveillance in the United States (553 KB, 85 pages).

Other CDC Publications

• The Epidemic of West Nile Virus in the United States, 2002 (284 KB, 10 pages)

• West Nile Virus and other Mosquito Borne Infections (1.38 MB, 6 pages)

• Herrington JE. Pre-West Nile Virus Outbreak: Perceptions and practices to prevent mosquito bites and viral encephalitis in the United States. Vector Borne and Zoonotic Diseases Journal, 2003;3(4):157-173. (261 KB, 17pages)

• National West Nile Virus Surveillance System, 2000: Final Plan (81 KB, 24 pages)

• CDC Data and Specimen Handling (DASH) section form 50.34 for submission of laboratory specimens (22 KB, 2 pages)








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http://www.cdc.gov/ncidod/eid/vol6no4/pdf/rappole.pdf

http://www.cdc.gov/ncidod/eid/vol5no5/hubalek.htm

http://www.cdc.gov/ncidod/eid/vol5no5/pdf/hubalek.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnvguidelines2003.pdf



http://www.cdc.gov/ncidod/dvbid/arbor/arboguid.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/OLearyetalVBZD2004.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv_othermosqinfec.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/VBZD_Herrington_Dec_03.pdf



http://www.cdc.gov/ncidod/dvbid/westnile/resources/wn_final_plan_2000_05_26_31.pdf

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• West Nile Virus (WNV) Infection: Information for Clinicians

o PDF (151 KB/2 pages) o MS Word (98 KB/2 pages)

Publications Outside CDC

o Ary Farajollahi, Robert Gates, Wayne Crans, Nicholas Komar. Serologic Evidence of West Nile Virus and St. Louis Encephalitis Virus Infections in White-Tailed Deer (Odocoileus virginianus) from New Jersey, 2001,

(60 KB, 5 pages). Vector-Borne and Zoonotic Diseases. December, 2004; Vol. 4, No. 4, Pages 379-383.

o Martha Iwamoto, M.D., M.P.H., Daniel B. Jernigan, M.D., M.P.H., Antonio Guasch, M.D., et al. Transmission of West Nile Virus from an Organ Donor to Four Transplant Recipients. The New England Journal of Medicine. 2003;348:2196-2203.

o D,L. Morse, Perspective: West Nile Virus--Not a Passing Phenomenon.The New England Journal of Medicine. 2003;348:2173-2174.

o DA Martin, BJ Biggerstaff, B Allen, AJ Johnson, RS Lanciotti and JT Roehrig. 2002. Use of Immunoglibulin M Cross-reactions in Differential Diagnosis of Human Flaviviral Encephalitis Infections in the United States. Clinical and Diagnostic Laboratory Immunology 9(3):544-49.

o Biggerstaff, B. J., and Petersen, L. R. (2002), Estimated Risk of West Nile Virus Transmission through Blood Transfusion During an Epidemic in Queens, New York City, Transfusion, 42, 1019-1026.

o Anderson JF, Andreadis TG, Vossbrinck CR, et al. Isolation of West Nile virus from mosquitoes, crows, and a Cooper's hawk in Connecticut. Science. 1999;286:2331-2333.

o Campbell GL, Marfin AM, Lanciotti RS, and Gubler DG. West Nile virus. Lancet Infectious Diseases. 2002;2:519-29. (In PDF format [1.57 MB, 11 pages].) Reprinted with permission from Elsevier Science (The Lancet, 2002, Vol No. 2, 519-29) Lancet Infectious Diseases Homepage ScienceDirectTM

o Han LL, Popovici F, Alexander, Jr. JP, et al. Risk factors for West Nile virus infection and meningitis or encephalitis, Romania, 1996. Journal of Infectious Diseases. 1999;179:230-233.


http://www.cdc.gov/ncidod/dvbid/westnile/resources/fact_sheet_clinician.htm

http://www.cdc.gov/ncidod/dvbid/westnile/resources/fact_sheet_clinician_082102_0802.pdf

http://www.cdc.gov/ncidod/dvbid/westnile/resources/fact_sheet_clinician.doc

http://www.cdc.gov/ncidod/dvbid/westnile/resources/WNVFarajolllahiDeervbz2004.pdf



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http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-campbell-etal.pdf

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o Jai X-Y, Briese T, Jordan I, Rambaut A, et al. Genetic analysis of West Nile New York 1999 virus. Lancet. 1999;354:1971-1972.

o Komar N. West Nile viral encephalitis. Revue Scientifique et Technique 2000;191:66-76.

o Lanciotti RS, Kerst AJ, Nasci RS, et al. Rapid detection of West Nile virus from human clinical specimens, field-collected mosquitoes, and avian samples by a TaqMan reverse transcriptase-PCR assay. Journal of Clinical Microbiology 2000;38:4066-4071.

o Lanciotti RS, Roehrig JT, Deubel V, et al. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States. Science. 1999;286(5448):2333-2337.

o Mostashari F, Bunning ML, Kitsutani PT, et al. Epidemic West Nile encephalitis, New York, 1999: results of a household-based seroepidemiological survey. Lancet 2001;358:261-264.

o Nash D, Mostashari F, Fina A, et al. The outbreak of West Nile virus infection in the New York City area in 1999. New England Journal of Medicine 2001;3441:1807-1814.

o Petersen LR, Marfin AA. West Nile Virus: A Primer for the Clinician [Review] Annals of Internal Medicine 2002;137:173-179. (Also available in PDF format [287 KB, 7 pages].)

o Savage HM, Ceianu C, Nicolescu G, et al. Entomologic and avian investigations of an epidemic of West Nile fever in Romania in 1996, with serologic and molecular characterizations of a virus isolate from mosquitoes. American Journal of Tropical Medicine and Hygiene. 1999;61:600-611.

o Tsai TF, Popovici F, Cernescu C, Campbell GL, Nedelcu NI. West Nile encephalitis epidemic in southeastern Romania. Lancet. 1998;352:767-771.

Repellent Related Publications

o Updated Information regarding Insect Repellents

o New! Barnard DR, Xue RD. Laboratory evaluation of mosquito repellents against Aedes albopictus, Culex nigripalpus, and Ochlerotatus triseriatus (Diptera: Culicidae). J Med Entomol. 2004 Jul;41(4):726-30.


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http://www.annals.org/issues/v137n3/pdf/200208060-00009.pdf



o Fradin MS, Day JF. Comparative efficacy of insect repellents against mosquito bites. N Engl J Med. 2002;347(1):13-8. Access restricted. See NEJM homepage for access options.


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Recommendations for Protecting Outdoor Workers from West Nile Virus Exposure

The West Nile Virus (WNV) is most often spread to humans from the bite of an infected mosquito. Workers at risk of WNV exposure include those working outdoors when mosquitoes are biting—farmers, foresters, landscapers, groundskeepers and gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and other outdoor workers. Entomologists and other field workers are also at risk while conducting surveillance and other research outdoors.

Workers at risk should receive training that describes and reinforces the potential occupational hazards and risks of WNV exposure and infection. The importance of timely reporting of all injuries and illnesses of suspected occupational origin should be emphasized. A medical surveillance system should be in place which includes the reporting of symptoms consistent with WNV infection and employee absenteeism due to WNV infection.

Recommendations for employers of Outdoor Workers

Removing tires from the worksite helps to reduce mosquito populations.

Employers should protect their workers from WNV exposure by taking the following steps:

• Provide training that describes how WNV is transmitted and reinforces knowledge about the risks of WNV exposure and infection.

• Stress to workers the importance of reporting all work-related injuries and illnesses in a timely manner.

• Provide a medical surveillance system that monitors, records, and assesses the symptoms and absenteeism associated with WNV infection.

• Provide workers with protective clothing (long-sleeved shirts, long pants, and socks) and repellents to use on skin and clothing:

o Use repellents containing DEET (more than 20% DEET for longer protection), picaridin, or oil of lemon eucalyptus on both skin and clothing.

o Use permethrin on clothing only.

• Reduce worker exposure to mosquitoes by taking the following steps:

o Avoid having workers outdoors when mosquitoes are most active and biting (most often from dusk to dawn).



o Recommend that outdoor workers wear long-sleeved shirts, long pants, and socks when possible.

o If worker uniforms are provided, include long-sleeved shirts and long pants as options.

• Eliminate as many sources of standing water from the worksite as possible to decrease mosquito populations:

o Change the water every 4 to 5 days in animal drinking troughs, birdbaths, and other water containers.

o Scrub the sides of water containers to dislodge eggs.

o Add an aerator to ponds and water gardens to keep the water circulating, or add fish that will eat the mosquito larvae or adults.

o Remove discarded tires or keep them dry and under cover.

o Turn over, cover, store, or remove equipment such as tarps, buckets, barrels, wheelbarrows, and containers to prevent standing water.

o Place drain holes in containers that collect water and cannot be discarded.

o Clean out rain gutters.

o Remove debris (leaves, twigs, trash) from ditches.

o Fill in ruts and other areas that collect standing water.

Recommendations for workers Outdoor workers can reduce their risk of WNV exposure by taking the following steps:

Using an effective insect repellent helps prevent mosquito bites.

• Use insect repellent if you work outdoors when mosquitoes are biting:

o Apply insect repellent containing DEET (more than 20% DEET for longer protection), picaridin, or oil of lemon eucalyptus to exposed skin and to clothing.

o Use permethrin on clothing only.

o Carefully follow label directions for repellent use.

o Do not apply pump or aerosol products directly to the face. Instead, spray these products onto the hands and carefully rub them over the face, avoiding the eyes and mouth.

o Use a repellent that provides protection for the amount of time that you will be outdoors and reapply it as needed. The percentage of active ingredient in the repellent determines the length of protection.

o Wash skin treated with insect repellent with soap and water after returning indoors.

• Use protective clothing if you work outdoors when mosquitoes are biting:

o Wear long-sleeved shirts, long pants, and socks.

o Spray clothing with products containing DEET, picaridin, oil of lemon ecualyptus, or permethrin, as mosquitoes may penetrate thin clothing.

o Use permethrin repellents on clothing as directed; do not apply them directly to skin.

o Wash clothing treated with insect repellent before wearing it again.

o Do not apply repellent to skin that is covered by clothing.



• Avoid handling dead animals when possible. If you must handle them, take the following precautions:

o Use tools such as shovels to avoid direct contact with the animals.

o Wear medical examination gloves that provide a protective barrier between your skin and blood or other body fluids:

Wear two pairs of gloves if one pair alone might tear.

Wear the medical examination gloves as the inner pair.

Make sure that any latex gloves used are reduced-protein, powder-free gloves to reduce workers’ exposure to allergy-causing proteins.

Wear cotton or leather work gloves as the outer pair when heavy work gloves are needed.

Discard both inner and outer gloves immediately after use.

Remember that cotton, leather, and other absorbent gloves are not protective when worn alone.

o If gloves are not available, use a plastic bag, which may act as a protective barrier between the animal and your skin.

Recommendations for Protecting Laboratory, Field, and Clinical Workers from West Nile Virus

Exposure

Occupational Risk

The West Nile Virus (WNV) is most often spread to humans from the bite of an infected mosquito. Therefore, persons working outdoors when mosquitoes are actively biting are at risk of infection and should be educated about this occupational health issue and available recommendations (link to Recommendations to Prevent West Nile Virus Infection in Outdoor Workers).

In addition to outdoor workers, workers in many other occupations are at potential risk of exposure to WNV-infected persons, animals, fluids, or tissues. Workers at risk include laboratory diagnosticians, researchers, and technicians, veterinarians and their staff, wildlife rehabilitators, ornithologists, wildlife biologists, pathologists, zoo and aviary curators, health care workers, emergency response and public safety personnel, public health employees, and workers


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in related occupations. For example, workers are at risk of WNV infection if their skin is penetrated or cut while performing necropsies or handling WNV-infected tissues or fluids. Turkey breeder and alligator farm workers have been infected with WNV. The mode of transmission to these farm workers is uncertain.

The following recommendations are for laboratory, field, and clinical workplaces in which transmission of WNV may occur by means other than mosquito bite. Until further studies determine the risk of WNV infection from exposure to infected persons, animals, fluids, or tissues, it is prudent public health practice to minimize such potentially infectious contacts. These are basic recommendations to reduce exposure to blood and other tissues from WNV-infected animals or persons. More stringent protective equipment and work practices should be used when warranted. Biosafety guidelines are available for working with WNV and other microbiological agents in the laboratory.

Recommendations for employers

West Nile Virus Guide ------------------------------------------------------------------------------------------------------------

• Provide training that describes how WNV is transmitted and reinforces the potential hazards and risks of WNV exposure and infection.

• Provide appropriate personal protective equipment that provides barrier protection including gloves, gowns, safety glasses, and/or face shields.

o Alternatives to powdered latex gloves should be provided.

• Stress to employees the importance of timely reporting of all injuries and illnesses.

• Provide a medical surveillance system that monitors, records, and assesses:

o symptoms consistent with WNV infection

o laboratory incidents or accidents involving possible WNV exposure

o employee absenteeism

Recommendations for workers

• Use personal protective equipment that provides barrier protection including gloves, gowns, safety glasses, and/or face shields to avoid dermal and mucous membrane contact with blood and other tissues.

o Workers conducting necropsies should wear gloves that prevent cutting injuries, such as stainless steel mesh gloves, in addition to medical examination gloves.

• Wash hands and other skin surfaces with soap and water immediately after contact with blood or other tissues, after removing gloves, and before leaving the workplace.

• Minimize the generation of aerosols.

• Handle sharp instruments carefully during use.

• Use medical devices with safety features when available to avoid sharps-related injuries.

• Avoid recapping needles.

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• Dispose of sharp instruments carefully after use.

• Report to the supervisor all needlestick and other sharps-related injuries.

• Report to the supervisor any laboratory incidents or accidents involving possible WNV exposure.

• Report to the supervisor any symptoms consistent with WNV infection.

Conclusion The fact is that there really isn’t a conclusion to the West Nile Virus story. The conclusion would be to be continually vigilant, watching always for new developments and to be on a continual watch for the ever present mosquito. Information is your best weapon, with the proper knowledge you can learn to keep mosquito populations in control. You can protect yourself and your loved ones with the proper repellants when outside. You can avoid the time of day when mosquitoes are present in their greatest quantities. Most of the information in this book comes from US government agencies that have spent a lot of time and money investigating the west nile virus, in an attempt to provide the public with information they can use to protect themselves from mosquito bites and the resulting west nile virus. Use this information and you’ll stay safe. If you’ve only read 10 pages, you already know more about the west nile virus than most of the world. My wish is that you use this information and pass it on. Thanks for reading.


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