Influenza A virus is a major public health threat, killing more than 30, 000 people per year in the USA. Novel influenza virus strains caused by genetic drift and viral recombination emerge periodically to which humans have little or no immunity, resulting in devastating pandemics. Influenza A can exist in a variety of animals; however, it is in birds that all subtypes can be found. These subtypes are classified based on the combination of the virus coat glycoproteins hemagglutinin (HA) and neuraminidase (NA) subtypes. During 1997, an H5N1 avian influenza virus was determined to be the cause of death in 6 of 18 infected patients in Hong Kong. The more recent virulent strain of H5N1 is now seen in Africa and Europe, as well as in Southeast Asia. There is some evidence of human to human spread of this virus, but it is thought that the transmission efficiency was fairly low. The influenza membrane ion channel (M2) is a small transmembrane protein that regulates the pH inside the virion during viral entry into the cell and protects the newly synthesized hemagglutinin during their transport through low pH cellular compartments. It has been suggested as a target of neutralizing antibodies.
