A brief introduction to influenza A virus in swine.

Influenza A viruses (IAV) of the Orthomyxoviridae virus family cause one of the most important respiratory diseases in pigs as well as humans. Repeated outbreaks and rapid spread of genetically and antigenically distinct IAVs represent a considerable challenge for animal production and public health. This overlap between human and animal health is a prime example of the "One Health" concept. Although only subtypes of H1N1, H1N2, and H3N2 are endemic in swine around the world, considerable diversity can be found not only in the hemagglutinin (HA) and neuraminidase (NA) genes, but in the other 6 genes as well. Human and swine IAV have demonstrated a particular propensity for interspecies transmission in the past century, leading to regular and sometimes sustained, incursions from man to pig and vice versa. The diversity of IAV in swine remains one of the critical challenges in diagnosis and control of this important pathogen for swine health, and in turn contributes to a significant public health risk.