Avian influenza A virus

Avian influenza viruses (AIVs) are enveloped, negative-sense, single-stranded RNA viruses in the family of Orthomyxoviridae. In poultry, AIVs are classified as highly pathogenic avian influenza (HPAI) or low pathogenic avian influenza (LPAI), based on lethality for chickens. HPAI causes severe disease and high death rates and LPAI cause mild disease.

AIVs are further subdivided into subtypes based on the surface glycoprotein expression of hemagglutinin (HA) and neuraminidase (NA). The HA determines host specificity and serves as the virus receptor–binding protein, and the NA is embedded in the M2 ion channel protein in the host-derived lipid envelope.

Wild birds, especially waterfowl, are considered the main natural reservoir and source for all subtypes of AIVs. Antibodies to AIVs have also been detected in numerous species of mammals (including wild rodents such as rats and mice, raccoons, foxes, mink, deet, pigs, cats, and dogs), which can also potentially introduce the virus to poultry flocks.

Incubation period: The incubation period is 3 to 5 days in general but may be longer. Maximal incubation period is 21 days as defined by the OIE Terrestrial Animal Health Code.

Survival in the Environment: AIVs remain infectious after 24 to 48 hours on nonporous environmental surfaces and less than 12 hours on porous surfaces.