This is what a swine flu virus looks like in the f - swine flu refers to influenza caused by any virus of the family orthomyxoviridae that is endemic to pic populations. known strains in swine influenza virus are classified as either influenzavirus c or one of the subtypes of influenzavirus a people who work with poultry and swine, especially people with intense exposures are at risk of infection from these animals if the animals carry a strain that is also able to infect humans. siv can mutate into a form that allows it to pass from human to human. the strain responsible for the 2009 swine flu outbreak is believed to have undergone this mutation.