Influenza A Virus

Influenza A virus causes influenza in birds and some mammals, and is the only species of the Alphainfluenzavirus genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon.

Avian influenza—known informally as avian flu or bird flu is a variety of influenza caused by viruses adapted tobirds. The type with the greatest risk is highly pathogenic avian influenza (HPAI). Bird flu is similar to swine flu, dog flu, horse flu and human flu as an illness caused by strains of influenza viruses that have adapted to a specific host. Out of the three types of influenza viruses (A, B, and C), influenza A virus is a zoonoticinfection with a natural reservoir almost entirely in birds. Avian influenza, for most purposes, refers to the influenza A virus.