Avian influenza is flu infection in birds. The disease is of concern to humans, who have no immunity against it. The virus that causes this infection in birds can change (mutate) to infect humans. Such mutation could start a deadly worldwide epidemic.

The first avian influenza virus to infect humans directly occurred in Hong Kong in 1997, during an avian flu epidemic on the island. This outbreak was linked to chickens and classified as avian influenza A (H5N1).

Human cases of avian influenza A (H5N1) have now been reported in Asia, Africa, the Pacific, Europe and the near East, Indonesia, and Vietnam. Around 400 people have become sick with this virus. However, a little over 60% of those who became ill have died.

The more the avian flu virus spreads, the greater the chances of a worldwide outbreak. There is a tremendous concern that H5N1 poses an enormous pandemic threat.

Farmers and other people working with poultry, as well as travelers visiting affected countries, have a higher risk for getting the bird flu. Handling an infected bird can cause infection. People who eat raw or undercooked poultry meat, eggs, or blood from these birds are also at an increased risk for avian influenza.

The avian flu virus (H5N1) has been shown to survive in the environment for long periods of time. Infection may be spread simply by touching contaminated surfaces. Birds who recover from the flu can continue to shed the virus in their feces and saliva for as long as 10 days.

Health care workers and household contacts of patients with avian influenza may also be at an increased risk of the bird flu.