English: Schematic structure of influenza A virus (IAV). The envelope of the IAV particle, which is derived from the host cell plasma membrane, contains three trans-membrane proteins; two surface glycoproteins designated as hemagglutinin (HA) and neuraminidase (NA) and the proton channel matrix protein 2 (M2). The matrix protein 1 (M1) underlies the inner surface of the viral envelope and associates with NEP and viral ribonucleoprotein complexes (vRNPs). The eight vRNPs comprise eight negative-strand RNA segments associated with the nucleoprotein (NP) and three RdRp polymerase subunits (PA, PB1, PB2).