Avian influenza is an infectious disease caused by influenza A virus that occurs in poultry and wild birds. The virulence of different avian influenza virus subtypes is very different, and different strains of the same subtype and strain have different virulence when infecting different birds. Non-pathogenic strains and low pathogenic strains often only cause mild respiratory symptoms after infection. However, highly pathogenic avian influenza spreads rapidly, with short course of disease and high mortality (75% ~ 100%), resulting in huge economic losses.

The disease can be spread through many diseases, and blood-sucking insects can also spread viruses. Under natural conditions, viruses existing in nasal secretions and feces have great protection because of the protection of organic matter. The virus can still be isolated from wet feces 105 days after the sick chickens were eliminated. The virus can live for 18 days in feathers and 18 months in frozen poultry meat and bone marrow. Influenza viruses can often be isolated from lakes and ponds with birds. The virus has been isolated from guinea fowl, geese, pheasants, starlings, seagulls and seabirds. In the artificial inoculation experiment, cats, ferrets, monkeys and people can all be infected with influenza virus from poultry. Therefore, it is of great significance to prevent the outbreak of the disease.