What is the difference between pandemic H1N1 2009 and swine influenza?
Classical swine influenza is a well-known disease of pigs, caused by a distinct group of influenza A subtypes and strains. Different subtypes and variants are found in different parts of the world, but classical swine influenza is believed to occur worldwide. Infections with these classical swine influenza viruses, although capable of rapidly spreading within a herd, cause very low mortality or no mortality at all in infected herds, and are often of concern due to production losses, as pigs sick with influenza do not gain weight as quickly as unaffected pigs. Human infection with these known swine influenza viruses has occurred, but has been an uncommonly described event and usually associated with close contact with live pigs.
