Avian Influenza (Bird Flu)

Avian influenza (AI) or bird flu is a group of viruses that occur naturally in birds. A virus is pathogenic if it can cause illness or death. Some AI viruses can infect birds but not cause many bird illnesses or death. Other AI viruses, termed highly pathogenic avian influenza (HPAI), can cause large numbers of bird illnesses and deaths. Currently there is concern about one of these viruses, known as highly pathogenic H5N1, because it is causing severe disease in chickens and other poultry on several continents. It has also been found in wild birds in the same areas. In some instances, people who have had close contact with sick poultry have also become infected and gotten very sick. Approximately half of the people known to be infected have died.

Although officials are watching closely, this severe form of bird flu has not been found in the United States. It is important to remember that right now almost everyone who got sick with avian flu had close contact with infected poultry.

Both human and avian influenza viruses are constantly changing. There is concern that highly pathogenic H5N1 could change into a form easily spread from birds to humans and then from human to human.

If this were to happen, what is known as an influenza pandemic could occur.

Learn more about Avian (Bird) Influenza

Avian H7N9 Influenza

Avian H5N1 Influenza

Educational Materials

More Information

To learn more about other animal-related human health issues, visit the zoonoses main page.