What is avian influenza?
Avian influenza (AI)--the bird flu--is a virus that infects wild birds (such as ducks, gulls and shorebirds) and domestic poultry (such as chickens, turkeys, ducks and geese). There is a flu for birds just as there is for humans and, as with people, some forms of the flu are worse than others.
AI viruses are classified by a combination of two groups of proteins: the hemagglutinin or H proteins, of which there are 16 (H1-H16), and neuraminidase or N proteins, of which there are 9 (N1-N9).
AI strains also are divided into two groups based upon the ability of the virus to produce disease in poultry: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI).