Before 1889, H1 has been the main flu virus circulating in humans. However, in 1889, a new strain of H2 flu emerged in Russia and spread around the world, killing about 1 million people. Then, the 1918 influenza pandemic (known as Spanish flu) was an unusually deadly influenza pandemic, the first of the two epidemics involving H1N1 influenza virus. In 1931, H1N1 flu was first isolated from a pig in Iowa (USA). Then, it was isolated at Mill Hill in London. In 1976, H1N1 virus was transferred from pigs to humans and killed US army recruit and after year appeared in north-east China and started circulating in human causing seasonal flu in every subsequent year. In 1998 the predecessor of the 2009 H1N1 swine flu virus emerged in the US as a hybrid of human, bird, and swine flu viruses. The first cases of a new type of swine flu (in 2009) were reported in California and Texas in late March.