Additional information about avian influenza surveillance in wild birds is available at the USGS National Wildlife Health Center external icon. outbreaks of avian influenza in birds is available from USDA’s APHIS webpage external icon. Global avian influenza surveillance data is available from the World Organization for Animal Health website at Avian Influenza – OIE – World Organisation for Animal Health external icon. There are genetic and antigenic differences between the influenza A virus subtypes that typically infect only birds and those that can infect birds and people. HPAI and LPAI designations do not refer to or correlate with the severity of illness in cases of human infection with these viruses both LPAI and HPAI A viruses have caused mild to severe illness in infected humans. HPAI A(H5) and A(H7) virus infections in poultry also can spill back into wild birds, resulting in further geographic spread of the virus as those birds migrate. While some wild bird species can be infected with some HPAI A(H5) or A(H7) virus subtypes without appearing sick, other HPAI A(H5) and A(H7) virus subtypes can cause severe disease and mortality in some infected wild birds as well as in infected poultry.īoth HPAI and LPAI viruses can spread rapidly through poultry flocks. HPAI A(H5) or A(H7) virus infections can cause disease that affects multiple internal organs with mortality up to 90% to 100% in chickens, often within 48 hours. However, ducks can be infected without any signs of illness. Highly Pathogenic Avian Influenza (HPAI): Highly pathogenic avian influenza viruses cause severe disease and high mortality in infected poultry. Only some avian influenza A(H5) and A(H7) viruses are classified as HPAI A viruses, while most A(H5) and A(H7) viruses circulating among birds are LPAI A viruses.
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The categories refer to molecular characteristics of a virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting pdf icon external icon. They also can become infected through contact with surfaces that are contaminated with virus from infected birds.Īvian influenza A viruses are classified into the following two categories: low pathogenicity avian influenza (LPAI) A viruses, and highly pathogenic avian influenza (HPAI) A viruses. Susceptible birds become infected when they have contact with the virus as it is shed by infected birds. Infected birds can shed avian influenza A viruses in their saliva, nasal secretions, and feces.
However, avian influenza A viruses are very contagious among birds, and some of these viruses can sicken and even kill certain domesticated bird species, including chickens, ducks and turkeys. Wild aquatic birds can be infected with avian influenza A viruses in their intestines and respiratory tract, but some species, such as ducks, may not get sick. Wild aquatic birds, especially dabbling ducks, are considered reservoirs (hosts) for avian influenza A viruses. Wild aquatic birds include waterbirds (waterfowl) such as ducks, geese, swans, gulls, and terns, and shorebirds, such as storks, plovers, and sandpipers. These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Avian influenza A viruses have been isolated from more than 100 different species of wild birds around the world. Avian influenza refers to disease in birds caused by infection with avian (bird) influenza (flu) Type A viruses.
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