Title: Avian Influenza A(H5N1) and Risks to Human Health
1Avian Influenza A(H5N1) andRisks to Human Health
Keiji Fukuda Global Influenza Programme World
Health Organization
- Technical Meeting on Highly Pathogenic Avian
Influenza - and Human H5N1 infection
- Rome
- 27 - 29 June 2007
2Major Public Health Threatsof Influenza
- Seasonal
- Greatest health impact over time
- Avian influenza H5N1 virus
- Most often direct/indirect zoonotic infection
from infected birds - Infrequently direct contact with an infected
person - Other exposures not clearly established
- Emergence of a human pandemic strain
- H5N1 most concern due to spread pathogenicity
- Another novel subtype possible
3Laboratory-confirmed human H5N1 cases, since 2003
312 cases190 deaths
4Phylogenetic tree based on H5 HA Strains in
yellow vaccine strains
Vietnam Thailand Cambodia
Vietnam/JP14/05
ck/Cambodia/013LC1b/05
Vietnam/1194/04
Clade 1
Vietnam/1203/04
Vietnam/HN30408/05
Thailand/16/04
Vietnam/JPHN30321/05
Hong Kong/213/03
Indonesia/CDC523/06
Indonesia/CDC699/06
Indonesia/CDC326/06
Indonesia/5/05
Clade 2.1
Indonesia/CDC184/05
Indonesia/7/05
dk/KulonProgoBBVET9/04
Indonesia
ck/Indonesia/CDC25/05
Indonesia/6/05
ck/Brebes/BBVET2/05
Indonesia/CDC625/06
Indonesia/CDC594/06
Karo cluster
ck/Dairi/BPPVI/05
ck/Yunnan/374/04
ck/Yunnan/115/04
dk/Guangxi/13/04
ck/Guangxi/12/04
ck/Yunnan/493/05
ck/Yunnan/447/05
whooping swan/Mongolia/244/05
bar headed gs/Qinghai/1A/05
Clade 2.2
Turkey/65596/06
Turkey/15/06
Iraq/207NAMRU3/06
Middle east Europe Africa
ck/Nigeria/641/06
mld/Italy/332/06
turkey/Turkey/1/05
Egypt/2782NAMRU3/06
Djibouti/5691NAMRU3/06
ck/Nigeria42/06
migratory dk/Jiangxi/2136/05
gs/Kazakhstan/464/05
ck/Krasnodar/01/06
Azerbaijan/011162/06
swan/Iran/754/06
dk/Laos3295/06
Anhui/1/05
Clade 2.3
Anhui/2/05
Japanese white-eye/Hong Kong/1038/06
ck/Malaysia935/06
China Laos
Vietnam/30850/05
Guangxi/1/05
dk/Hunan/15/04
qa/Guangxi/575/05
dk/Vietnam/Ncvdcdc95/05
migratory dk/Jiangxi/1653/05
Hong Kong/156/97
gs/Guangdong/1/96
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6Characteristics of confirmed H5N1 human cases
- MF 09
- All age groups affected
- Higher incidence in age group lt 40 years
- Case fatality 63
- Median duration of illness
- Onset - hospitalization 4 days
- Onset - death 9 days
- Clinical features
- Severe cases feature pneumonia, ARDS
- Asymptomatic infection appears rare
7Risk factors and exposuresH5N1 in humans
- Primary known exposures associated with infected
birds - Unprotected handling
- Sharing living areas
- Route of virus entry into humans uncertain
- Risk appears highest in countries with infected
birds where - Human contact with poultry is frequent
- Animal disease detection and/or control is a
challenge - No identifiable exposures for some cases
8Human-to-Human H5N1 Transmission
- Epidemiological diagnosis of exclusion
- Plausible epidemiological link
- No other probable exposures
- Viruses consistent
- " Limited human-to-human transmission cannot be
ruled out" - Typically associated with very close prolonged
contact between susceptible and severely ill
person - No occurrence of human-to-human transmission
capable of sustained community outbreaks
9Prevention and treatment of human H5N1 infection
- One H5N1 vaccine licensed but not yet field
tested - Others applications in submission
- Optimal antiviral treatment regimen is yet
unknown - Early oseltamivir treatment might reduce
H5N1-associated mortality - Antiviral resistance requires monitoring
- Limited evaluation of other therapies
- E.g, immuno-modulators, convalescent sera
10WHO Strategic Action Plan Pandemic Influenza
11WHO Global Influenza Surveillance Network
12Important Current Activities
- Implementation of IHR
- Continuing development of framework to facilitate
sharing of influenza viruses and related benefits - Maintain rapid global threat assessment
response - Clearer operating terms conditions
- Greater access of developing countries to
benefits - Short to long term solutions for improving
pandemic H5 vaccine situation - Stockpiles
- Global Pandemic Influenza Vaccine Action Plan
13H5N1 Cluster Graph
- Cluster
- Two or more epidemiologically linked cases
- At least one has a lab-confirmed H5N1 infection
- Inclusion of fatal probable cases
- Unexplained deaths linked epidemiologically to a
confirmed case (probable case)
Cases in clusters