Avian influenza refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses. These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Avian flu viruses do not normally infect humans. However, sporadic human infections with avian flu viruses have occurred following direct or close contact with infected poultry. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person. Illness in humans can range from mild to severe.
Because influenza viruses are constantly changing, it is critical to monitor the spread and circulation of these viruses among poultry and other birds, in order to understand the risk of spread to humans.
The best way to prevent infection with avian influenza A viruses is to avoid sources of exposure. Most human infections have occurred following direct or close contact with infected poultry. Because rare episodes of limited, non-sustained human-to-human transmission of HPAI H5N1 virus has been reported, persons should avoid sick patients who have suspected or confirmed HPAI H5N1 virus infection. To date, there have not been any reports of avian flu virus infections among wild birds, poultry, or other animals or humans in the United States.