The WHO recently alerted for avian influenza worldwide including India. Subtypes H5, H7, and H9 have all caused outbreaks of avian influenza in human populations. This article summarizes some historical outbreaks of avian influenza subtypes and current epidemiological burden worldwide. Influenza subtypes: Influenza viruses belong to Orthomyxoviridae family that comprises of three genera-influenza A, B, and C.
To classify into subtypes and characterize, the combinations of the surface hemagglutinin (HA) and neuraminidase (NA) protein are used. For influenza A viruses, there are 16 different HA and nine different NA subtypes which result in many possible HA and NA combinations. Recently, after the discovery of some pathogenic strains in different parts of the world, WHO updated the H5 haemagglutinin (HA) clade nomenclature. After careful analysis of all available H5 sequence data, this…
