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Avian Influenza A(H5N1) and Risks to Human Health

Avian Influenza A(H5N1) and Risks to Human Health. Technical Meeting on Highly Pathogenic Avian Influenza and Human H5N1 infection Rome 27 - 29 June 2007. Keiji Fukuda Global Influenza Programme World Health Organization. Major Public Health Threats of Influenza. Seasonal

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Avian Influenza A(H5N1) and Risks to Human Health

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  1. Avian Influenza A(H5N1) andRisks to Human Health Technical Meeting on Highly Pathogenic Avian Influenza and Human H5N1 infection Rome 27 - 29 June 2007 Keiji Fukuda Global Influenza Programme World Health Organization

  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. Characteristics of confirmed H5N1 human cases • M:F = 0:9 • All age groups affected • Higher incidence in age group < 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

  6. 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

  7. 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

  8. 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

  9. WHO Strategic Action Plan Pandemic Influenza 1 Reduce Human Exposure to H5N1 virus Intensify Rapid Containment operations 2 Strengthen Early Warning system 3 4 Build Capacity to cope with pandemic Coordinate Global Scientific Research and Vaccine Development 5

  10. WHO Global Influenza Surveillance Network

  11. 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

  12. 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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