Avian Influenza

Bird flu"similar to "swine flu," "dog flu," "horse flu," or "human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species influenza A virus. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds,


which is why for many purposes avian flu virus is the influenza A virus (note that the "A" does not stand for "avian").



Transmission
AIV is distributed world wide primarily by migration of different avian species. Many species of waterfowl are asymptomatic carriers of AIV. Waterfowl are believed to be the primary reservoirs for influenza A, serving as a source of infection for other birds within their migratory path.
Infected birds can shed the virus via their respiratory system, ocular secretions and feces. There are no known incidences of vertical transmission.
Although direct transmission of AIV from birds to humans is very rare AIV is considered a zoonotic disease, meaning it is capable of being passed from birds and animal to humans. It is also quite possible that humans can infect birds with AIV, however this has not been documented