Bird flu or avian influenza is a contagious disease of birds ranging from mild to severe form of illness. all birds are thought to be susceptible to avian influenza, though some species are more resistant to infection than others. Some forms of bird flu infection can cause illness to humans.

Bird flu is caused by 15 subtypes of influenza A virus affecting chicken, ducks and other birds. Viruses of low pathogenicity can, mutate into highly pathogenic viruses.

To date, all outbreaks of the highly infective form have been caused bu influenza A /H5N1 virus, the only subtype that cause severe outbreaks in humans.

Most Recent Situation and Cumulative Cases on Avian Influenza (WHO)