According to the CDC: Swine influenza is a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Influenza viruses that commonly circulate in swine are called “swine influenza viruses” or “swine flu viruses.” Like human influenza viruses, there are different subtypes and strains of swine influenza viruses. The main swine influenza viruses circulating in U.S. pigs in recent years have been, swine triple reassortant (tr) H1N1 influenza virus, trH3N2 virus, and trH1N2 virus. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza According to Wikipedia; A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3. The swine flu was initially seen in Mexico in April 2009, where the strain of the particular virus was a mixture from 3 types of strains. Six of the genes are very similar to the H1N2 influenza virus that was found in pigs around 2000. 59 million Americans contracted the disease in 2009. 265,000 were hospitalized and 12,000 died.