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THE INFLUENZA VIRUS

THE INFLUENZA VIRUS. ORTHOMYXOVIRIDAE. Influenza virus. Influenza C virus. Type A. Type B. Type C. Classification. RNA virus. Family:. Genus:. Types:. Kingsbury DW. In: Fields BN et al. , eds. Virology . 2nd Edn. New York: Raven Press; 1990: 1076–87.

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THE INFLUENZA VIRUS

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  1. THE INFLUENZA VIRUS

  2. ORTHOMYXOVIRIDAE Influenza virus Influenza C virus Type A Type B Type C Classification RNA virus Family: Genus: Types: Kingsbury DW. In: Fields BN et al., eds. Virology. 2nd Edn. New York: Raven Press; 1990: 1076–87. Photo courtesy of Linda Stannard, University of Cape Town, South Africa.

  3. Nucleocapsid: Nucleoprotein (NP)-RNA (7 or 8 segments) Internal antigens Matrix protein (M) Lipid bilayer Haemaglutinin (HA) Surface antigens Neuraminidase (NA) 80 to 120 nm Structure: segmented and enveloped viruses Kingsbury DW. In: Fields BN et al., eds. Virology. 2nd Edn. New York: Raven Press; 1990: 1076–87.

  4. Surface glycoproteins • Haemagglutinin • H or HA • responsible for pathogenicity of the virus • allows virus to adhere to endothelial cells in the respiratory tract • main determinant of immunity • Neuraminidase • N or NA • allows release of newly formed viruses within host • determinant of disease severity

  5. Influenza subgroups • Influenza A • highly infective • infects many species • causes widespread epidemics • Influenza B • found only in humans • capable of producing severe disease • causes regional epidemics • Influenza C • causes mild disease • humans are natural hosts, but isolates also found in pigs • does not cause epidemics

  6. The virus nomenclature Classification of the human influenza viruses For example:A / Beijing / 32 / 92 (H3N2) A virus type, here A Beijing place where the strain was isolated 32 strain number 92 year of first isolation H3N2 subtypes H3 and N2 virus type, here H3N2

  7. Occurrence of influenza A viruses Influenza A viruses 16 HA types 9 NA types Species affected humans, pigs, horses, birds, marine mammals In humans 3 HA types (H1, H2, H3) 3 NA types (N1, N2, N8) In birds all HA types all NA types

  8. By courtesy of APACIAsia-Pacific Advisory Committee on influenzawww.apaci-flu.com

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