Swine influenza is an infection caused by any one of several types of swine influenza viruses. 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 A known as H1N1, H1N2, H2N1, H911,H3N1, H3N2, and H2N3. The Swine flu was initially seen in humans in Mexico in 2009, where the strand of the particular virus was a marriage of 3 types of strands. Six of the genes are very similar to the H1N2 influenza virus that was found in pigs around 2000.