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, including the so-called "avian flu" or H5N1, can be found. These subtypes are classified based on the combination of the virus coat glycoproteins hemagglutinin (HA) and neuraminidase (NA) subtypes. One of the less studied proteins encoded by, but not incorporated in, the influenza virus is the nonstructural protein (NS) 1. NS1 counters cellular antiviral activities and acts as a virulence factor. It can bind to double-stranded RNA and sequester it from 2�?5�?OAS, preventing the activation of the RNAse L, which normally acts to degrade RNA and prevent virus replication. NS1 also binds to and inhibits the anti-viral protein kinase PKR.
