Avian Influenza is an infectious disease caused by influenza virus A whose subtypes(i.e.bird flu virus,such as H5N1 and H9N2) mainly infect birds but occasionally affect humans.It is classified as the top infectious disease by OIE(Office International des Epizooties i.e.the World Organization for Animal Health).It is of great significance to the prevention and control of its occurring and to human health that people know and recognize the epidemic of avian influenza and its viral characteristics,its ways of spread and initial symptoms and how to exterminate it and protect the body by making vaccine.