INFECTIOUS DISEASESINFECTIOUS DISEASESIN HONG KONG IN HONG KONG and and ITS PREVENTIONITS PREVENTION

Dr Margaret IPDr Margaret IPDept of MicrobiologyDept of Microbiology1717thth Jan 05 Jan 05

Definition of Infectious Disease:

““ An illness due to a specific An illness due to a specific infectious agent or its toxic products infectious agent or its toxic products that arises through transmission of that arises through transmission of that agent or its products from an that agent or its products from an infected person, animal, or reservoir infected person, animal, or reservoir to a susceptible host, either directly to a susceptible host, either directly or indirectly through an intermediate or indirectly through an intermediate plant or animal host, vector, or the plant or animal host, vector, or the inamimate environment”inamimate environment”

John M. Last Dictionary

The “chain of infection”

The infectious agentThe infectious agentThe means of transmissionThe means of transmissionThe hostThe host

Route of Transmission

VerticalVertical – Mother to foetus – Mother to foetus

HorizontalHorizontal

– – directdirect

ContactContact

InhalationalInhalational

IngestionIngestion

– – indirectindirect

via bugs eg mosquitoes, fleasvia bugs eg mosquitoes, fleas

HOSTHOST ORGANISMORGANISM

ENVIRONMENTENVIRONMENT

Infectious Diseases : A Dynamic Interaction

Causes of Infectious Causes of Infectious DiseaseDisease

BacteriaBacteria – – Staphylococcus aureusStaphylococcus aureus

VirusesViruses – Influenza virus, Hepatitis – Influenza virus, Hepatitis virusvirus

FungiFungi - - Candida spp., Aspergillus Candida spp., Aspergillus spp.spp.

Mycobacteria Mycobacteria - - M.tuberculosisM.tuberculosis, ,

ProtozoaProtozoa – – Entamoeba histolyticaEntamoeba histolytica

WormsWorms – Pork and beef tapeworms – Pork and beef tapeworms

Robert Koch, 1843-1910• Doctor and Founder of Medical Microbiology

• Experiments on ‘Germ theory of disease’

• Koch’s postulates

• Bacterial culture plate technique

• Microscopy of Bacteria

•Discovery of tubercle bacillus

• Isolation of bacteria causing cholera

大腸桿菌

幽門螺旋菌

乙型肝炎病毒 Source: Department of Microbiology, The Chinese University of Hong Kong

曲黴菌Source: Department of Microbiology, The Chinese University of Hong Kong

阿米巴變形蟲 蛔虫 ( 成年

)Source: Department of Microbiology, The Chinese University of Hong Kong

控制傳染病的健康機構

國際性組織 香港本地組織

世界衛生組織(WHO)

美國疾病控制中心(CDC)

疾病預防及控制部

食物環保衛生署

醫院管理局

疾病預防及控制部

(HA)(CHP) (FEHD

)

Infectious Diseases of New Concern

Additions to the Notifiable Diseases List, Hong Kong:

Severe Acute Respiratory Syndrome, 27 Severe Acute Respiratory Syndrome, 27 Mar 03Mar 03

Avian Influenza A, H5, 30 Jan 04Avian Influenza A, H5, 30 Jan 04 Japanese Encephalitis, 16 Jul 04Japanese Encephalitis, 16 Jul 04 Avian Influenza A (H7) and (H9), 30 Dec 04Avian Influenza A (H7) and (H9), 30 Dec 04

Electron Microscopy of Influenza virusElectron Microscopy of Influenza virus

1918

2001Avian InfluenzaAvian Influenza

Diseases of Current Concern

Diseases of Current Concern

http://www.cdc.gov/flu/

H1N1 H2N2 H3N?H1N1 H2N2 H3N?

1889 1900 1918 1957 1968 1977 1889 1900 1918 1957 1968 1977 CurrentCurrentH2N2 H3N8 H1N1 H2N2 H3N2 H1N1 H3N2 &H2N2 H3N8 H1N1 H2N2 H3N2 H1N1 H3N2 & H1N1H1N1

H3N2H3N2

H1N1H1N1

Influenza Pandemics

Droplet Transmission

• Droplets generated during coughing, sneezing, and talking,

• Deposited on host’s conjunctivae, nasal mucosa, or mouth

Influenza A, Prince of Wales Hospital 1996-Influenza A, Prince of Wales Hospital 1996-20012001

0

20

40

60

80

100

120

140

160

180

200

1996

-Jan Ap

r

Jul

Oct

1997

-Jan Ap

r

Jul

Oct

1998

-Jan Ap

r

Jul

Oct

1999

-Jan Ap

r

Jul

Oct

2000

-Jan Ap

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Jul

Oct

2001

-Jan Ap

r

Jul

Oct

No

. of C

ases

H3N2 Sydney

H3N2 Wuhan

( Epidemics due to antigenic drift )

Typing and Sub-typing of Influenza Typing and Sub-typing of Influenza VirusVirus

RNA (8 segments)

Nucleoprotein(A,B & C types)

Haemagglutinin (H)

Envelope

Neuraminidase (N)

MAN PIG HORSE BIRDMAN PIG HORSE BIRD

H typesH typesH1H1 √√ √√ √√ H2 H2 √√ √√ √√H3 H3 √ √ √√ √√H4 H4 √√H5 H5 √√ √√H6 H6 √√H7H7 √√ √√ √√H8 H8 √√H9H9 √√ √√H10-H15H10-H15 √√

N typesN typesN1N1 √√ √√ √√N2N2 √√ √√ √√N3N3 √√N4N4 √√ N5 N5

√√N6N6 √√N7N7 √√ √√N8N8 √√ √√ N9 N9

√√

Reassortment of Influenza Virus GenesReassortment of Influenza Virus Genes

H5H5N2N2

H3H3N2N2

H3H3N1N1

H5H5N1N1

H3H3N2N2

Infection of bothInfection of bothviruses into viruses into

the same cell the same cell

Cell cytoplasmCell cytoplasm

Genomic exchangeGenomic exchange

Progeny reassortantsProgeny reassortants256 different combinations256 different combinations

H5H5N1N1

AvianAvian

HumanHuman

Reassortment / Cross-species Reassortment / Cross-species TransmissionTransmission

06/04/97 06/04/97 3 chicken farms with H5N1 infection, 4500 chicken died3 chicken farms with H5N1 infection, 4500 chicken died

21/05/97 21/05/97 3 years old boy infected with influenza A, died3 years old boy infected with influenza A, died

18/08/97 18/08/97 confirmed to be confirmed to be H5N1H5N1- Dept. of Health, 2 universities, CDC formed expert committee- Dept. of Health, 2 universities, CDC formed expert committee

24/11/97 24/11/97 2 years old boy2 years old boy H5N1 H5N1 infected, lived infected, lived29/11/97 29/11/97 54 years old man died of54 years old man died of H5N1 H5N1 pneumonia pneumonia06/12/97 06/12/97 13 years old girl infected with13 years old girl infected with H5N1 H5N1, multi-organ failure, died, multi-organ failure, died09/12/97 09/12/97 20 years old Filipino woman 20 years old Filipino woman H5N1H5N1 infected, critical infected, critical

27/12/97 27/12/97 confirmed 18 infected with confirmed 18 infected with H5N1H5N1, 3 suspected, 3 suspected 6 patients died6 patients died

29/12/97 29/12/97 killing of all 1.4 million chickens in Hong Kongkilling of all 1.4 million chickens in Hong KongUNTIL NOW UNTIL NOW no new cases of H5N1 no new cases of H5N1

Aug, 97 to Jan 98Aug, 97 to Jan 98Surveillance of avian flu in poultry showedSurveillance of avian flu in poultry showed

20% 20% H5N1H5N1 5% 5% H9N2H9N2

28/02/9928/02/99 4 years old girl with 4 years old girl with H9N2 H9N204/03/9904/03/99 1 year old girl with 1 year old girl with H9N2H9N2

Outbreak of Avian H5N1 & H9N2 Influenza in Hong Outbreak of Avian H5N1 & H9N2 Influenza in Hong Kong Kong

H5N1 Avian Influenza H5N1 Avian Influenza CasesCasesYEARYEAR LOCATIONLOCATION CASESCASES DEATHS DEATHS

(%)(%)

19971997 Hong Hong KongKong

1818 6 (33%)6 (33%)

20032003 ChinaChina 22 1 (50%)1 (50%)

2003 - 42003 - 4 VietnamVietnam 2727 20 (74%)20 (74%)

2003 - 42003 - 4 ThailandThailand 1717 12 (71%)12 (71%)

TOTALTOTAL 7474 39 (53%)39 (53%)(Accessed www.medscape.com/viewarticle/493090, 11Nov04)

Control Measures for Influenza Control Measures for Influenza Inactivated Influenza VaccineInactivated Influenza Vaccine

Made by inactivating purified vaccine strain Made by inactivating purified vaccine strain viruses grown in eggs viruses grown in eggs

New vaccine strains are made as reassortants New vaccine strains are made as reassortants with high growth virus carrying the necessary H with high growth virus carrying the necessary H & N Ag& N Ag

Constituent viruses in vaccine determined by Constituent viruses in vaccine determined by circulating strains as suggested by WHO (Feb circulating strains as suggested by WHO (Feb for north, Sep for south) for north, Sep for south)

Global prevalence data and new strains originate Global prevalence data and new strains originate from WHO influenza surveillance networkfrom WHO influenza surveillance network

Influenza Vaccination 2004-5 Northern Hemisphere (WHO Recommendation on Vaccine (WHO Recommendation on Vaccine

Composition)Composition)

An A/Fujian/411/2002 (H3N2)-like virus

An A/New Caledonia/20/99(H1N1)-like virus

A B/Shanghai/361/2002-like virus

(or B/Jiangsu/10/2003)

Control Measures for Control Measures for Influenza Influenza Vaccine ApplicationVaccine Application

WHO Recommendations:• Residents of institutions for elderly & disabled• Any age with chronic illness• Age > 65yr• HCWs contact with high-risk persons• Household contacts of high-risk persons

Influenza Vaccination Influenza Vaccination Efficacy and Side EffectsEfficacy and Side Effects

Efficacy varies from 70-90% protection in Efficacy varies from 70-90% protection in young adults to 60-70% in the elderlyyoung adults to 60-70% in the elderly

vaccine reduces 70% hospitalization & 85% of vaccine reduces 70% hospitalization & 85% of death in the elderlydeath in the elderly

in nursing homes, vaccine can reduce in nursing homes, vaccine can reduce hospitalization by 50%, pneumonia 60% & hospitalization by 50%, pneumonia 60% & death by 75-80%death by 75-80%

very little side effect, <1/3 with soreness, 5-10% very little side effect, <1/3 with soreness, 5-10% experience mild side effects e.g. headache or experience mild side effects e.g. headache or low grade feverlow grade fever

Control Measures for Avian InfluenzaControl Measures for Avian Influenza Human disease surveillanceHuman disease surveillance Control at source…poultry Control at source…poultry Hygiene improvement in farms and Hygiene improvement in farms and

marketsmarkets Education and publicityEducation and publicity Import ControlImport Control Contingency & pandemic planningContingency & pandemic planning Development of diagnostic tests & Development of diagnostic tests &

vaccinevaccine Segregation policy for poultry processingSegregation policy for poultry processing

Prevention of Infectious Prevention of Infectious DiseasesDiseases

Breaking the chain of infectionBreaking the chain of infection• Isolation & QuarantineIsolation & Quarantine

• Remove source of infectionRemove source of infection• Modifying host eg. vaccinationModifying host eg. vaccination• Modifying environmentModifying environment

• Eg. Improve sanitation, eradication Eg. Improve sanitation, eradication of vectors eg mosquitoesof vectors eg mosquitoes

•Handwashing / alcohol handrub•Cap•Eye protection •Masks (N95/surgical)•Gloves•Gowns •Uniforms

Hospital Isolation

Prevention of Infectious Prevention of Infectious DiseasesDiseases

Breaking the chain of infectionBreaking the chain of infection• Isolation & QuarantineIsolation & Quarantine

• Remove source of infectionRemove source of infection• Modifying host eg. vaccinationModifying host eg. vaccination• Modifying environmentModifying environment

• Eg. Improve sanitation, eradication Eg. Improve sanitation, eradication of vectors eg mosquitoesof vectors eg mosquitoes

Control Measures Control of Source - chicken culling

Continuous H5N1 virus isolation from Continuous H5N1 virus isolation from wholesale market and chicken farms wholesale market and chicken farms

No effective antiviral treatment & vaccineNo effective antiviral treatment & vaccine

Influenza season coming in Feb - MarchInfluenza season coming in Feb - March

1.5 millions birds killed from 29 - 31 Dec 1.5 millions birds killed from 29 - 31 Dec 9797

Control Measures Control Measures Market and Farm HygieneMarket and Farm Hygiene

Issue guidelines to all operators of food Issue guidelines to all operators of food premises, fresh provision shops and premises, fresh provision shops and market stalls for handling poultry market stalls for handling poultry

Clean farms and wholesale & retail outletsClean farms and wholesale & retail outlets

System to ensure H5N1-free chicken:System to ensure H5N1-free chicken:– quarantinequarantine– certification certification – blood tests at borderblood tests at border– labelinglabeling– hold-and-salehold-and-sale

Influenza A H5N1 in Hong Influenza A H5N1 in Hong Kong Kong Lessons LearnedLessons Learned

International collaboration is essentialInternational collaboration is essential

Institution of effective measures Institution of effective measures especially in livestock controlespecially in livestock control

Continuous surveillance of influenza Continuous surveillance of influenza activity in both human and animalsactivity in both human and animals

Environmental Control and Education

http://www.fehd.gov.hk/events/mos/anti_mos_2004.html

Signs and Symptoms in 57 Signs and Symptoms in 57 Hospitalized Cases of DHF, Puerto Hospitalized Cases of DHF, Puerto Rico, 1990 - 1991Rico, 1990 - 1991

* Minimum estimate, search was not uniform for all patients** Only 2 (3.5%) cases had severe hemorrhagic manifestations

SIGNS AND SYMPTOMS FREQUENCY* %

Fever 57 100 %Rash 27 47.4%Hepatomegaly 6 10.5%Effusions 3 5.3%Frank shock 3 5.3%Coma 2 3.5%Any hemorrhage** 57 100 %

Warning Signs for Dengue Shock

When Patients Develop DSS:• 3 to 6 days after onset of symptoms

When Patients Develop DSS:• 3 to 6 days after onset of symptoms

Initial Warning Signals:• Disappearance of fever• Drop in platelets• Increase in hematocrit

Initial Warning Signals:• Disappearance of fever• Drop in platelets• Increase in hematocrit

Alarm Signals:• Severe abdominal pain• Prolonged vomiting• Abrupt change from fever to hypothermia• Change in level of consciousness (irritability or somnolence)

Alarm Signals:• Severe abdominal pain• Prolonged vomiting• Abrupt change from fever to hypothermia• Change in level of consciousness (irritability or somnolence)

Four Criteria for DHF:• Fever• Hemorrhagic manifestations• Excessive capillary permeability• 100,000/mm3 platelets

Four Criteria for DHF:• Fever• Hemorrhagic manifestations• Excessive capillary permeability• 100,000/mm3 platelets

Mean Annual Number of DHF CasesThailand, Indonesia and Vietnam, by Decade

* Provisional data through 1998

020406080

100120140160180200

Rep

orte

d C

ases

(Tho

usan

ds)

1950s 1960s 1970s 1980s 1990s*

Reasons for Dengue Reasons for Dengue Expansion in the WorldExpansion in the World

Extensive vector infestation, with Extensive vector infestation, with declining vector controldeclining vector control

Unreliable water supply systemsUnreliable water supply systems Increasing non-biodegradable Increasing non-biodegradable

containers and poor solid waste containers and poor solid waste disposaldisposal

Increased air travelIncreased air travel Increasing population density in urban Increasing population density in urban

areasareas

The Challenge

Achieve active community involvementAchieve active community involvement Solicit input from the earliest program Solicit input from the earliest program

planning stagesplanning stages Encourage community ownershipEncourage community ownership Programs that emphasize telling Programs that emphasize telling

communities what to do, without communities what to do, without involving them or taking their views into involving them or taking their views into account, are not effectiveaccount, are not effective

True community participation is keyTrue community participation is key

Prevention of Infectious Prevention of Infectious DiseasesDiseases

Breaking the chain of infectionBreaking the chain of infection• Isolation & QuarantineIsolation & Quarantine

• Remove source of infectionRemove source of infection• Modifying host eg. vaccinationModifying host eg. vaccination• Modifying environmentModifying environment

• Eg. Improve sanitation, eradication Eg. Improve sanitation, eradication of vectors eg mosquitoesof vectors eg mosquitoes

http://www.sc.edu/library/spcoll/nathist/jenner.html

Hong Kong Immunization Hong Kong Immunization ProgrammeProgramme

AgeAge Immunization recommendedImmunization recommended

NewbornNewborn BCG, Polio 1, Hepatitis B vaccineBCG, Polio 1, Hepatitis B vaccine

1 month1 month Hepatitis B vaccineHepatitis B vaccine

2-4 months2-4 months DPT (Diphtheria, pertussis, tetanus)DPT (Diphtheria, pertussis, tetanus)

Polio trivalentPolio trivalent

3-5 months3-5 months DPTDPT

4-6 months4-6 months DPT, Polio trivalentDPT, Polio trivalent

6 months6 months Hepatitis B vaccineHepatitis B vaccine

1 year 1 year MMR (Measles, mumps, rubella)MMR (Measles, mumps, rubella)

1 ½ yr1 ½ yr DPT, Polio trivalentDPT, Polio trivalent

Primary 1Primary 1 DT, Polio trivalent, MMRDT, Polio trivalent, MMR

Primary 6Primary 6 DT, Polio trivalentDT, Polio trivalent

Thank you Thank you for for Listening!Listening!