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Avian Influenza H5N1 (Bird Flu) Virus


Avian influenza viruses usually infect birds, but some strains can also infect humans. Humans that get avian influenza usually have come in direct contact with infected birds, birds that have died from avian influenza, or bird droppings. "Bird flu" typically refers to an influenza A virus type called H5N1.

There are two types of influenza A H5N1: highly pathogenic and low pathogenic. The H5N1 strain commonly called "bird flu" is the highly pathogenic type. This virus strain typically infects wild waterfowl, such as ducks, and is now found in Asia, Africa, and Europe. Birds infected with highly pathogenic H5N1 virus can experience very mild to very severe symptoms, including death. Rarely, domestic birds, such as chickens, also get infected with "bird flu" H5N1. In poultry, it causes severe illness and death. In rare instances, the "bird flu" virus can be transmitted to humans primarily through direct exposure to infected birds or the environment where the birds live. When people get infected with "bird flu" virus, it can cause severe illness and death. Currently, avian influenza H5N1 does not pass easily between people, so it has not become a pandemic influenza strain.

Current Global Situation

The highly pathogenic avian influenza H5N1 strain ("bird flu") has not been found in the United States to date. It also has not been found in the rest of the western hemisphere, including Canada, Mexico, and Central and South America. There is ongoing surveillance throughout the US and the world to look for "bird flu" in migratory waterfowl. In the US, the US Department of Agriculture, US Department of the Interior and the US Department of Health and Human Services work together on this surveillance. Their findings are available here.

Highly pathogenic avian influenza H5N1 ("bird flu") has been found in Asia, Africa, and Europe. International travelers should be aware of all infectious diseases they may encounter in their travels, including avian influenza. To learn about diseases in the countries you are visiting, click here.

To see a timeline of highly pathogenic avian influenza H5N1 human and animal infections around the world since it was found in 1996, click here.

Other Resources

Avian Influenza (Bird Flu) (CDC)
Avian Influenza (WHO)
Highly Pathogenic Avian Influenza Early Detection Data System (NBII)
Wildlife Damage Management (USDA National Wildlife Disease Program)
National Wildlife Health Center (USGS)
Georgia Response Plan for HPAI in Poultry (Georgia Department of Agriculture)