bird flu

Overview
What is bird flu?
Bird flu is an infection caused by a type of avian influenza virus. Although there are many types of bird flu, the type that now concerns health workers is the H5N1 bird flu virus. This virus is found in wild birds. Most of the time, wild birds do not get sick from the virus. But wild birds can easily pass the virus to birds that are being raised for food-such as chickens, ducks, and turkeys-and cause them to get very sick.
Usually, bird flu virus is not passed from birds to people. But since 1997, some people have become sick with this serious, deadly type of bird flu. Most of these infections have been in Asian countries among people who have had close contact with farm-raised birds.
What causes bird flu?
Bird flu is caused by an infection with a virus. After a wild bird infects a farm-raised bird, the virus can easily and quickly spread among hundreds or thousands of birds. Sick birds must then be killed to stop the virus from spreading.