Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza that regularly cause outbreaks of influenza among pigs. Swine flu viruses do not normally infect humans. However, human infections of swine flu do occur, and cases of human-to-human communicability of swine flu has been documented.From December 2005 – February 2009, a total of 12 human infections of swine influenza were reported from 10 states in the United States. Since March 2009, a number of confirmed human cases of a new strain of swine influenza A (H1N1) virus infection in California and Texas have been identified. An investigation into these cases is ongoing.