[A negative-strand linear single-strand RNA virus with an 8 segment genome. Virions are enveloped and usually spherical or pleomorphic, 80-120 nm in diameter. Subtyping is based on the antigenic properties of the hemagglutinin and neuraminidase proteins. Influenza type A viruses can infect people, birds, pigs, horses, and other animals, but wild birds are the natural hosts for these viruses. ( NCI )]
UMLS (CSP) C0029347