AVIAN FLU
Avian influenza (bird flu) is caused by a strain of influenza virus that originally infected birds. Infected birds include chickens, ducks, and geese, among others.
There are several strains of avian flu; the H5N1 avian flu virus is the cause of concern since it has led to several deaths in people, mostly in Asia. Another type of avian flu that causes illness in people is called H7N9. To date, avian flu has primarily spread from bird to bird and much less commonly from bird to human; human-to-human transmission has occurred rarely. Most humans who became infected with avian flu had direct contact with sick or dead poultry or wild birds or had very recently visited a live poultry market. No human cases of avian influenza have been described in the United States or elsewhere in North America.
Avian flu is frequently severe, and there is little natural immunity in the human population. At least one antiviral medicine (oseltamivir) might improve the chance of surviving the infection. (See 'Antiviral treatment' above.)
There is a vaccine to prevent avian flu. The vaccine is not commercially available but has been stockpiled by the United States government in case it is needed in the future.
Updated information about avian influenza is available from the United States Centers for Disease Control and Prevention website.