Avian Influenza (Avian Flu, Bird Flu)

March 2024 Outbreak in Dairy Cattle

In March 2024, an avian flu outbreak was detected in dairy cattle. See more information on that outbreak.

Avian influenza (AI), also called avian flu or bird flu, is caused by a group of viruses that occur naturally in wild birds. A virus is pathogenic if it can cause illness or death. Some avian influenza viruses can infect birds but not cause many bird illnesses or deaths. Other avian influenza viruses, termed highly pathogenic avian influenza (HPAI), can cause large numbers of illnesses and deaths in chickens and other poultry and some species of wild birds. These viruses can also infect some mammals including dairy cattle.

In some instances, people who have had close contact with sick poultry have also become infected with certain strains of avian influenza and gotten very sick. Some people known to be infected have died. It is important to remember that right now almost everyone who has gotten sick with avian influenza has had close contact with infected animals, especially poultry.

Animal health officials are watching closely for avian influenza in poultry, wild birds and mammals in the United States. Early detection of AI in poultry and wild birds is important to prevent the spread of avian influenza, especially into commercial poultry flocks, and to protect human health.

Both human and avian influenza viruses are constantly changing. There is concern that avian influenza viruses that are known to have infected humans 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

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