ERVW-1 and infection: This hypothesis is corroborated by the facts that similar trends have been observed for other cell receptor binding enzymes, such as the neuraminidase of the influenza virus subtypes A H1N1 and A H3N2 [28] and that a similar intra-individual evolution occurs to the envelope glycoprotein of hepatitis C virus after the acute phase of the infection to escape from the host immune response and establish persistent (i.e., chronic) infection [29, 30].