The Facts
Avian influenza is a type of influenza or "flu" that occurs in all species of birds. The virus that causes avian influenza - more commonly called "bird flu" - exists naturally in many wild birds, including wild waterfowl, without causing the condition in them; these birds are called carriers. Normally, the virus is associated with birds raised on poultry farms and less often, with pigs.
Most people may not immediately make the connection between avian influenza and humans. Avian influenza is rare in humans. When it does infect a human, the virus often causes serious illness or death. Recently, avian influenza has been getting more and more attention from medical authorities around the globe. A new subtype of the virus called H5N1 can cause disease with a high rate of mortality (death) in humans.