What is H1H1. H1N1 formerly known as 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 with swine flu do occur. In the current swine flu outbreak that began in Mexico in April 2009, cases of human-to-human spread of swine flu viruses have been documented. Cases of human infection with swine influenza A (H1N1) viruses were first reported in Southern California and near San Antonio, Texas. Other U.S. states have reported cases of swine flu infection in humans. Cases have been reported internationally –Canada (confirmed), New Zealand, Israel, France etc...(suspected cases)-as well.