Influenza A virus subtype H3N2, an enveloped virus of the Orthomyxoviridae family, is a respiratory infection in birds and mammals, and is an important cause of human influenza. In birds, humans, and pigs, the virus has mutated into many strains. Its derives from the forms of the two kinds of proteins on the surface of its coat, hemagglutinin(HA) and neuraminidase(NA). Influenza A viruses are further classified into 16HA (H1-H16) and 9NA (N1-N9) serotypes based on the antigenic characteristics of HA and NA envelop glycoprotein. The extent of infection into host organisms are determined by HA, which interacts with cell surface proteins containing oligosaccharides with terminal sialyl residues.