H1N1 - info

The 2009 flu pandemic is a global outbreak of a new strain of influenza A virus subtype H1N1, identified in April 2009, commonly referred to as "swine flu", which is transmitted between humans. It is thought to be a mutation—more specifically, a reassortment—of four known strains of influenza A virus subtype H1N1: one endemic in humans, one endemic in birds, and two endemic in pigs (swine). Experts now assume that the virus "most likely" emerged from pigs in Asia, and the virus was carried to North America by infected people. There is further evidence that the new strain has been circulating among pigs, possibly among multiple continents, for many years prior to its transmission to humans.