Clinical Definition

Avian flu, or bird flu, is an infectious disease caused by avian flu (bird influenza A) viruses. Many different strains of the virus exist in the intestines of migrating wild birds, and some of these strains can cause mild to serious symptoms. These viruses typically infect only other fowl, but on rare occasions, they have infected mammals, even humans.

In Our Own Words

Bird flu, also known as avian influenza, is an infectious disease caused by influenza A viruses that are found naturally among birds. Usually the infected wild birds only infect each other, but sometimes, domesticated birds such as chickens and turkeys can become infected. When people come into direct contact with infected poultry or objects containing infected secretions, such as animal droppings or saliva, they can also become infected.

Among the better-known strains of bird flu virus is the H5N1, found in many areas of Asia, and for which a vaccine has been developed. A newer bird flu virus, H7N9, was reported in China in 2013. Seasonal influenza is much more common and likely to occur in the United States than any bird flu, but authorities are watchful, since an outbreak of an emerging strain is always possible.