swine influenza (h1n1) is a very contagious respiratory disease caused by a strain of the influenza type a virus. swine influenza (h1n1) or swine flu (h1n1) originally occurred only in pigs or rarely in those who were around pigs. however a new strain of the swine flu (h1n1) virus has been able to spread from person to person. outbreaks of the new swine flu (h1n1) started to occur between humans in march 2009.
what is swine influenza (h1n1)?