 [ Symptoms ] what is the swine flu h1n1 virus [ Disease ] this is a virus found in pigs that causes swine influenza the swine flu h1n1 virus is different from the human flu virus there are many different strains of swine flu h1n1 virus e g h1n1 h3n2 h1n1 is the most common usually a swine flu h1n1 virus infects only pigs or in rare cases those around pigs but a new type of swine flu h1n1 virus has been spreading from person to person