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INFECTIOUS DISEASES
IN HONG KONG
and
ITS PREVENTION
Dr Margaret IP
Dept of Microbiology
17th Jan 05
Definition of Infectious Disease:
“An illness due to a specific infectious
agent or its toxic products that arises
through transmission of that agent or its
products from an infected person, animal,
or reservoir to a susceptible host, either
directly or indirectly through an
intermediate plant or animal host, vector,
or the inamimate environment”
John M. Last Dictionary
The “chain of infection”
 The
infectious agent
 The means of
transmission
 The host
Route of Transmission
Vertical – Mother to foetus
Horizontal
– direct
Contact
Inhalational
Ingestion
– indirect
via bugs eg mosquitoes, fleas
Infectious Diseases : A
Dynamic Interaction
HOST
ORGANISM
ENVIRONMENT
Causes of Infectious Disease
Bacteria – Staphylococcus aureus
Viruses – Influenza virus, Hepatitis virus
Fungi - Candida spp., Aspergillus spp.
Mycobacteria - M.tuberculosis,
Protozoa – Entamoeba histolytica
Worms – 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
Source: Department of Microbiology,
The Chinese University of Hong Kong
曲黴菌
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
疾病預防及
控制部
世界衛生組織
(WHO)
美國疾病控制中心 疾病預防及
控制部
(CDC)
(CHP)
醫院管理局
(HA)
食物環保
衛生署
(FEHD)
Infectious Diseases of New Concern
Additions to the Notifiable Diseases List, Hong Kong:




Severe Acute Respiratory Syndrome, 27 Mar 03
Avian Influenza A, H5, 30 Jan 04
Japanese Encephalitis, 16 Jul 04
Avian Influenza A (H7) and (H9), 30 Dec 04
Electron Microscopy of Influenza virus
1918
2001
Avian Influenza
http://www.cdc.gov/flu/
Influenza Pandemics
1889
H2N2
1900
H3N8
1918
H1N1
1957
H2N2
1968
H3N2
1977
H1N1
Current
H3N2 & H1N1
H1N1
H3N2
H1N1
H2N2
H3N?
Droplet Transmission
• Droplets generated during
coughing, sneezing, and talking,
• Deposited on host’s
conjunctivae, nasal mucosa, or
mouth
Influenza A, Prince of Wales Hospital 1996-2001
( Epidemics due to antigenic drift )
200
H3N2 Sydney
180
160
120
H3N2 Wuhan
100
80
60
40
20
Oct
Jul
Apr
2001-Jan
Oct
Jul
Apr
2000-Jan
Oct
Jul
Apr
1999-Jan
Oct
Jul
Apr
1998-Jan
Oct
Jul
Apr
1997-Jan
Oct
Jul
Apr
0
1996-Jan
No. of Cases
140
Typing and Sub-typing of Influenza
Virus
MAN PIG
Haemagglutinin (H)
RNA (8
segments)
Nucleoprotein
(A,B & C types)
Envelope
Neuraminidase (N)
H types
H1
√
H2
√
H3
√
H4
H5
√
H6
H7
√
H8
H9
√
H10-H15
N types
N1
√
N2
√
N3
N4
N6
N7
N8
HORSE BIRD
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√ N5
√
√
√
√ N9
√
Reassortment of Influenza Virus Genes
Avian
Progeny reassortants
256 different combinations
Cell cytoplasm
H5N1
H5N2
Infection of both
viruses into
the same cell
H5N1
Genomic exchange
H3N1
H3N2
Human
H3N2
Reassortment / Cross-species
Transmission
Outbreak of Avian H5N1 & H9N2 Influenza in Hong
Kong
06/04/97 3 chicken farms with H5N1 infection, 4500 chicken died
21/05/97 3 years old boy infected with influenza A, died
18/08/97 confirmed to be H5N1
- Dept. of Health, 2 universities, CDC formed expert committee
24/11/97
29/11/97
06/12/97
09/12/97
2 years old boy H5N1 infected, lived
54 years old man died of H5N1 pneumonia
13 years old girl infected with H5N1, multi-organ failure, died
20 years old Filipino woman H5N1 infected, critical
27/12/97 confirmed 18 infected with H5N1, 3 suspected
6 patients died
29/12/97 killing of all 1.4 million chickens in Hong Kong
UNTIL NOW no new cases of H5N1
Aug, 97 to Jan 98
Surveillance of avian flu in poultry showed
20% H5N1 5% H9N2
28/02/99 4 years old girl with H9N2
04/03/99 1 year old girl with H9N2
H5N1 Avian Influenza Cases
YEAR
LOCATION
CASES
1997
Hong Kong
18
DEATHS
(%)
6 (33%)
2003
China
2
1 (50%)
2003 - 4
Vietnam
27
20 (74%)
2003 - 4
Thailand
17
12 (71%)
74
39 (53%)
TOTAL
(Accessed www.medscape.com/viewarticle/493090,
11Nov04)
Control Measures for Influenza
Inactivated Influenza Vaccine

Made by inactivating purified vaccine strain
viruses grown in eggs

New vaccine strains are made as reassortants
with high growth virus carrying the necessary
H & N Ag

Constituent viruses in vaccine determined by
circulating strains as suggested by WHO (Feb
for north, Sep for south)

Global prevalence data and new strains
originate from WHO influenza surveillance
network
Influenza Vaccination
2004-5 Northern Hemisphere
(WHO Recommendation on Vaccine
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 Influenza
Vaccine 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
Efficacy and Side Effects

Efficacy varies from 70-90% protection in
young adults to 60-70% in the elderly

vaccine reduces 70% hospitalization & 85% of
death in the elderly

in nursing homes, vaccine can reduce
hospitalization by 50%, pneumonia 60% &
death by 75-80%

very little side effect, <1/3 with soreness, 5-10%
experience mild side effects e.g. headache or
low grade fever
Control Measures for Avian Influenza

Human disease surveillance

Control at source…poultry

Hygiene improvement in farms and
markets

Education and publicity

Import Control

Contingency & pandemic planning

Development of diagnostic tests &
vaccine

Segregation policy for poultry
processing
Prevention of Infectious Diseases
Breaking the chain of infection
• Isolation & Quarantine
• Remove source of infection
•
•
Modifying host eg. vaccination
Modifying environment
• Eg. Improve sanitation, eradication of
vectors eg mosquitoes
Hospital Isolation
•Handwashing /
alcohol handrub
•Cap
•Eye protection
•Masks (N95/surgical)
•Gloves
•Gowns
•Uniforms
Prevention of Infectious Diseases
Breaking the chain of infection
• Isolation & Quarantine
• Remove source of infection
•
•
Modifying host eg. vaccination
Modifying environment
• Eg. Improve sanitation, eradication of
vectors eg mosquitoes
Control Measures
Control of Source - chicken culling

Continuous H5N1 virus isolation from
wholesale market and chicken farms

No effective antiviral treatment & vaccine

Influenza season coming in Feb - March

1.5 millions birds killed from 29 - 31 Dec
97
Control Measures
Market and Farm Hygiene

Issue guidelines to all operators of food
premises, fresh provision shops and
market stalls for handling poultry

Clean farms and wholesale & retail outlets

System to ensure H5N1-free chicken:
–
–
–
–
–
quarantine
certification
blood tests at border
labeling
hold-and-sale
Influenza A H5N1 in Hong
Kong
Lessons Learned

International collaboration is essential

Institution of effective measures
especially in livestock control

Continuous surveillance of influenza
activity 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
Hospitalized Cases of DHF, Puerto
Rico, 1990 - 1991
SIGNS AND SYMPTOMS FREQUENCY* %
Fever
Rash
Hepatomegaly
Effusions
Frank shock
Coma
Any hemorrhage**
57
27
6
3
3
2
57
100 %
47.4%
10.5%
5.3%
5.3%
3.5%
100 %
* Minimum estimate, search was not uniform for all patients
** Only 2 (3.5%) cases had severe hemorrhagic manifestations
Warning Signs for Dengue
Shock
Four Criteria for DHF:
• Fever
• Hemorrhagic manifestations
• Excessive capillary
permeability
• 100,000/mm3 platelets
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)
When Patients Develop
DSS:
• 3 to 6 days after onset of
symptoms
Mean Annual Number of DHF Cases
Reported Cases
(Thousands)
Thailand, Indonesia and Vietnam, by Decade
200
180
160
140
120
100
80
60
40
20
0
1950s
1960s
* Provisional data through 1998
1970s
1980s
1990s*
Reasons for Dengue
Expansion in the World





Extensive vector infestation, with
declining vector control
Unreliable water supply systems
Increasing non-biodegradable
containers and poor solid waste
disposal
Increased air travel
Increasing population density in
urban areas
The Challenge





Achieve active community involvement
Solicit input from the earliest program
planning stages
Encourage community ownership
Programs that emphasize telling
communities what to do, without
involving them or taking their views into
account, are not effective
True community participation is key
Prevention of Infectious Diseases
Breaking the chain of infection
• Isolation & Quarantine
• Remove source of infection
•
•
Modifying host eg. vaccination
Modifying environment
• Eg. Improve sanitation, eradication of
vectors eg mosquitoes
http://www.sc.edu/library/spcoll/nathist/jenner.html
Hong Kong Immunization Programme
Age
Newborn
1 month
2-4 months
Immunization recommended
BCG, Polio 1, Hepatitis B vaccine
Hepatitis B vaccine
DPT (Diphtheria, pertussis, tetanus)
Polio trivalent
3-5 months DPT
4-6 months DPT, Polio trivalent
6 months
Hepatitis B vaccine
1 year
MMR (Measles, mumps, rubella)
1 ½ yr
DPT, Polio trivalent
Primary 1
DT, Polio trivalent, MMR
Primary 6
DT, Polio trivalent
Thank you
for
Listening!