Keywords: Influenza subtypes.svg The various strains of influenza that have infected the human population in the 20th century Data taken from figure 2 of cite journal Palese P Influenza old and new threats Nat Med 10 12 Suppl S82 7 2004 December 15577936 10 1038/nm1141 Own 21 13 30 April 2009 UTC Fvasconcellos thumb 200px left Spanish thumb 200px left 体中文 thumb 200px left 繁體中文 Influenza |