Avian influenza belongs to the family Orthomyxoviridae. The influenza viruses are unstable in the environment. They can be inactivated by extreme changes of temperature, heat, nonisotonic conditions, and dryness.
The virus has two major surface glycoproteins called hemagglutinin (HA) and neuraminidase (NA). These give the virus its antigenic diversity. They are used in labeling different subtypes using the letters H and N and the appropriate numbers (ie. H5N1). These subtypes have the ability to exhange genomic information in a process called genetic reassortment.