Genetic characterization of influenza viruses from influenza-related hospital admissions in the St. Petersburg and Valencia sites of the Global Influenza Hospital Surveillance Network during the 2013/14 influenza season

Influenza A antigenic variants differed between St. Petersburg and Valencia, and A(H3N2) clade 3C.2 viruses were characterized by more amino acid differences from the vaccine strain, especially at the antigenic sites.