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Dengue fever

Dengue fever is a virus-based disease spread by mosquitoes.

Dengue fever is caused by one of four different but related viruses. It is spread by the bite of 

mosquitoes, most commonly the mosquito Aedesaegypti, which is found in tropic and subtropic

regions. This includes parts of:

  Indonesian archipelago into northeastern Australia

  South and Central America

  Southeast Asia

  Sub-Saharan Africa

Dengue fever is being seen more in world travelers.

Dengue fever should not be confused with Dengue hemorrhagic fever, which is a separate

disease that is caused bythe same type of virus but has much more severe symptom

the same type of virus but has much more severe symptoms.

Dengue fever also known as breakbone fever, is an infectious tropical

disease caused by the dengue virus. Symptoms include fever , headache, muscle and

 joint pains, and a characteristic skin rash that is similar to measles. In a small proportion

of cases the disease develops into threatening dengue hemorrhagic fever, resulting in 

bleeding, low levels of blood platelets and blood plasma leakage, or the life-

into dengue shock syndrome, where dangerously low blood pressure occurs.

Signs and symptoms

Dengue fever begins with a sudden high fever, often as high as 104 - 105 degrees Fahrenheit.

Infection with the dengue virus may be subclinical (no apparent symptoms) or may cause illness ranging from a mild

fever to a severe, even fatal condition, ie.denguehaemorrhagic fever or dengue shock syndrome.

The symptoms may last up to a week. Some people may experience a resurgence of fever and other symptoms that

may last another 2-3 days.

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Typically, people infected with dengue virus are asymptomatic (80%) or only have mild symptoms such as

an uncomplicated fever .[1][2][3]

 Others have more severe illness (5%), and in a small proportion it is life-

threatening.[1][3]

 The incubation period(time between exposure and onset of symptoms) ranges from 3 –14

days, but most often it is 4 –7 days.[4]

 Therefore, travelers returning from endemic areas are unlikely to

have dengue if fever or other symptoms start more than 14 days after arriving home.[5]

 Children often

experience symptoms similar to those of the common coldand gastroenteritis (vomiting and

diarrhea),[6]

 but are more susceptible to the severe complications.[5]

 

A flat, red rash may appear over most of the body 2 - 5 days after the fever starts. A second rash, which looks like

the measles, appears later in the disease. Infected people may have increased skin sensitivity and are very

uncomfortable.

Symptoms are most commonly seen in adults and older children. Young children may show no symptoms. Symptoms

may include: 

  sudden onset of fever (lasting three to seven days)

  intense headache (especially behind the eyes)

  muscle and joint pain (ankles, knees and elbows)

  unpleasant metallic taste in mouth, loss of appetite, vomiting, diarrhoea, abdominal pain

  flushed skin on face and neck, fine skin rash as fever subsides

  rash on arms and legs, severe itching, peeling of skin and hair loss

  minor bleeding (nose or gums) and heavy menstrual periods

  extreme fatigue

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Dengue fever 

The typical rash seen in Dengue Fever 

Dengue haemorrhagic fever symptoms 

This is a rare complication of dengue in Australia. More commonly seen in children aged under 15 years, but can

occur in adults. Symptoms include:

  same signs as dengue fever 

  2-5 days after onset of fever, rapid deterioration and cardiovascular disease

  perhaps shock and sometimes death.

Other symptoms include:

  Headache (especially behind the eyes)

  Fatigue

  Joint aches

  Muscle aches

  Nausea

  Swollen lymph nodes

  Vomiting

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 Types of dengue

There are four types of dengue viruses that cause dengue fever worldwide - Dengue 1, 2, 3 and 4. A person infected

with one type of dengue will subsequently only be immune to that type. They will not be immune to other types of 

dengue and will, in fact, be at risk of developing severe symptoms if they contract another type of dengue.

Figures

The dengue mosquito found in Australia

On the mainland of North Queensland, one mosquito transmits the dengue virus: Aedesaegytpi (dengue mosquito).

In Australia, this mosquito is currently only found in inland and coastal population centres of Queensland. There is a

potential however for Aedesaegypti to establish itself in other areas such as the Northern Territory, Western Australia,

South-east Queensland and New South Wales.

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. Characteristics of Aedes Mosquitoes

 Aedes .Aedes mosquitoes bite in daylight. They breed in fresh stagnant , or brackish water.

Aedesaegypti , on e of t he most important disease transmitters, breed almost entirely on old

tires, t in cans, flo wer vases, a n d other similar man made cont ainers. The larvae h a n g at an

angle to t he surface of th e water. The adult rest sa nd feeds with its body parallel to t he

surface. 

Only female Aedes mosquito feeds on blood. This is because they need the protein found in

blood to produce eggs. Male mosquitoes feed only on plant nectar. On average, a femalemosquito can lay about 300 eggs during her life span of 14 to 21 days.

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Lifecycle of Aedes Mosquito

Life cycle: complete metamorphosis with 4 stages (egg, larva, pupa and adult) 

Mosquito Egg Raft

Adult mosquito generally lays eggs on water surface or its adjacent sites   Development of eggs takes 2 to 3 days 

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Mosquito Larva

Aquatic animal without leg

With four stages of development

Comes up to the water surface to take atmospheric air with its spiracle at the 8th

segment 

Mosquito Pupa 

Non-feeding aquatic form

Has to come up to the water surface to breathe usually

Life span is 2 to 3 days

Mosquito Adult

Body can be divided as head, thorax and abdomen

A pair of compound eyes and antennae as well as mouthparts on its head   A pair of jointed legs on each segment of the thorax and a pair of wings

The abdomen is composed of ten segments 

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Transmission

The mosquito Aedesaegypti  feeding off a human host

Dengue virus is primarily transmitted by Aedes  mosquitoes, particularly A. aegypti  . They bite primarily

during the day. Mosquito bites and sucks blood containing the virus from an infected person. And passos

the virus to healthy people when it bites them. 

Epidemiology

See also :  Dengue fever outbreaks 

Dengue distribution in 2006.

Red: Epidemic dengue and Ae. aegypti  

 Aqua: Just Ae. aegypti  

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Most people with dengue recover without any ongoing problems.[23]

 The mortality is 1 –5% without

treatment,[5]

 and less than 1% with adequate treatment;[23]

 however severe disease carries a mortality of 

26%.[5]

 Dengue is endemic in more than 110 countries.[5]

 It infects 50 to 100 million people worldwide a

year, leading to half a million hospitalizations,[1]

 and approximately 12,500 –25,000 deaths.[6][30]

 

The most common viral disease transmitted by arthropods,[12]

 dengue has a disease burdenestimated to

be 1600 disability-adjusted life years per million population, which is similar to other childhood and

tropical diseases such as tuberculosis.[13]

  As a tropical disease dengue is deemed only second in

importance to malaria,[5]

 though the World Health Organization counts dengue as one of 

sixteen neglected tropical diseases.[31]

 

Until 2003, dengue was classified as a potential  bioterrorism agent, but subsequent reports removed this

classification as it was deemed too difficult to transfer and only caused hemorrhagic fever  in a relatively

small proportion of people.[33]

 

History

The first record of a case of probable dengue fever is in a Chinese medical encyclopedia from the  Jin

Dynasty (265 –420 AD) which referred to a "water poison" associated with flying insects.[36][37]

 There have

been descriptions of epidemics in the 17th century, but the most plausible early reports of dengue

epidemics are from 1779 and 1780, when an epidemic swept Asia, Africa and North America.[37]

 From

that time until 1940, epidemics were infrequent.[37]

In 1906, transmission by the Aedes mosquitoes was confirmed, and in 1907 dengue was the second

disease (after  yellow fever ) that was shown to be caused by a virus.[38]

 Further investigations by John

Burton Cleland and Joseph Franklin Siler  completed the basic understanding of dengue transmission.[38]

 

Research

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Public health officers releasing P. reticulata  fry into an artificial lake in the Lago Norte district of  Brasília, Brazil, as part of a

vector control effort.

Research efforts to prevent and treat dengue include various means of vector control,[43]

 vaccine

development, and antiviral drugs.[27]

 

There are ongoing programs working on a dengue vaccine to cover all four serotypes .[27]

 One of the

concerns is that a vaccine could increase the risk of severe disease through antibody-dependent

enhancement.[44]

 The ideal vaccine is safe, effective after one or two injections, covers all serotypes, does

not contribute to ADE, is easily transported and stored, and is both affordable and cost-effective.[44]

  As of 

2009, a number of vaccines were undergoing testing.[13][33][44]

 It is hoped that the first products will be

commercially available by 2015.[27]

 

Prevention

 A 1920s photograph of efforts to disperse standing water and thus decrease mosquito populations

There are no approved vaccines for the dengue virus.[1]

 Prevention thus depends on control of and

protection from the bites of the mosquito that transmits it.[14][27]

 The World Health Organization

recommends an Integrated Vector Control program consisting of five elements: (1) Advocacy, social

mobilization and legislation to ensure that public health bodies and communities are strengthened,

(2) collaboration between the health and other sectors (public and private), (3) an integrated approach to

disease control to maximize use of resources, (4) evidence-based decision making to ensure any

interventions are targeted appropriately and (5) capacity-building to ensure an adequate response to the

local situation.[14]

 

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The primary method of controlling A. aegypti is by eliminating its habitats.[14]

 This is done by emptying

containers of water or by adding sand granular  insecticides or  biological control agents to places that

mosquitoes could potentially breed, such as flower vases and places where stagnant water could not be

removed. Cover all gully/floor. Reducing open collections of water through environmental modification is

the preferred method of control, given the concerns of negative health effect from insecticides and greater 

logistical difficulties with control agents.[14]

 People can prevent mosquito bites by wearing clothing that

fully covers the skin, using mosquito netting while resting, and/or the application of  insect

repellent (DEET being the most effective).[16]

 Ask a relative or close friend to check your home

regularly for stagnant water if you are going away for a long period of time. 

Treatment

There is no specific treatment for dengue fever. You will need fluids if there are signs of dehydration.

Acetaminophen (Tylenol) is used to treat a high fever. Avoid taking aspirin. 

Dengue fever treatment 

  See a doctor / general practitioner (GP) immediately.

  Wear insect repellent. If you have dengue fever, mosquitoes that bite you may pass dengue on to other 

people.

  Drink plenty of liquids and take paracetamol for fever and pain. Do not take aspirin because it can affectblood clotting.

Dengue haemorrhagic fever treatment 

 All patients with dengue haemorrhagic fever need to be hospitalised for fluid therapy and monitoring.

Doctors and health professionals can refer to Dengue haemorrhagic fever: diagnosis, treatment, prevention and

control (2nd edition. Geneva : World Health Organization, 1997) for detailed information on dengue symptoms and

treatment.

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References

  Gubler DJ (2010). "Dengue viruses". In Mahy BWJ, Van Regenmortel MHV. Desk Encyclopedia of Human and 

Medical Virology . Boston: Academic Press. pp. 372 –82. ISBN 0-12-375147-0. 

  WHO (2009). Dengue Guidelines for Diagnosis, Treatment, Prevention and Control . Geneva: World Health

Organization. ISBN 9241547871. 

  Naides SJ. Arthropod-borne viruses causing fever and rash syndromes. In: Goldman L, Ausiello D, eds.Cecil

 Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 405. 

Review Date: 8/28/2009.

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine,

University of Washington School of Medicine; and Jatin M. Vyas, MD, PhD, Instructor in Medicine, Harvard Medical School,

Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA,

Medical Director, A.D.A.M., Inc.

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THANK YOU!