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Avian Influenza A(H5N1) and Risks to Human Health

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Title: Avian Influenza A(H5N1) and Risks to Human Health


1
Avian 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

2
Major 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

3
Laboratory-confirmed human H5N1 cases, since 2003

312 cases190 deaths
4
Phylogenetic 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
5
(No Transcript)
6
Characteristics 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

7
Risk 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

8
Human-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

9
Prevention 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

10
WHO Strategic Action Plan Pandemic Influenza
11
WHO Global Influenza Surveillance Network
12
Important 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

13
H5N1 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
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