What is Swine Flu?: The H1N1 Virus

Swine influenza (also called H1N1) is a viral infection caused by one of several types of swine influenza virus. Swine influenza virus (SIV) is any strain of the influenza family of viruses that is endemic in pigs. Swine flu (swine influenza) is a respiratory disease caused by viruses that infect the respiratory tract of pigs and result in nasal secretions, a barking-like cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1.