Avian Influenza A(H5N1) and Risks to Human Health

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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

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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

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Laboratory-confirmed human H5N1 cases, since 2003

312 cases190 deaths
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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
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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

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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

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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

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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

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WHO Strategic Action Plan Pandemic Influenza
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WHO Global Influenza Surveillance Network
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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

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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