Influenza A Virus (subtype H1N1)

Influenzavirus A is a genus of the Orthomyxoviridae family of viruses and is a negative sense, single-stranded, segmented RNA virus. Based on the antigenicity of the glycoproteins, influenza A viruses are subdivided into sixteen H (H1-H16) and nine N (N1-N9) subtypes. A standard nomenclature for influenza virus isolates lists the influenza virus type (A or B), the host species (omitted if human origin), the geographical site, year of isolation, and the HA and NA subtype, for example: A/California/14/2009 (H1N1).

The main antigenic determinants of influenza A and B viruses are the hemagglutinin (HA) and neuraminidase (NA) transmembrane glycoproteins. Projections of HA and NA cover the surface of the virus particle. NA forms a tetramer with an average molecular weight of 220 kDa (~55 kDa per monomer). The matrix (M) protein of influenza A virus is one of the two group-specific internal proteins of the virion, The non-structural protein (NP) exists as a homeodimer (molecular weight of 52 kDa) consisting of two identical monomers (each ~26 kDa).