Swine influenza

Electron microscope

Swine influenza (also called swine flu, hog flu, Mexican flu and pig flu) refers to influenza caused by those strains ofinfluenza virus, called swine influenza virus (SIV), that usually infect (is endemic in) pigs As of 2009 these strains are all found in Influenza virus and the subtypes of Influenza virus.Swine influenza is common in pigs in the midwestern United States (and occasionally in other states), Mexico, Canada, South America, Europe (including the United Kingdom, Sweden, and Italy), Kenya, Mainland China, Taiwan, Japan and other parts of eastern Asia.

Transmission of swine influenza virus from pigs to humans is not common and properly cooked pork poses no risk of infection. When transmitted, the virus does not always cause humaninfluenza and often the only sign of infection is the presence of antibodies in the blood, detectable only by laboratory tests. When transmission results in influenza in a human, it is called zoonotic swine flu. People who work with pigs, especially people with intense exposures, are at risk of catching swine flu. However, only about fifty such transmissions have been recorded since the mid-20th century, when identification of influenza subtypes became possible. Rarely, these strains of swine flu can pass from human to human. In humans, the symptoms of swine flu are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.

The 2009 flu outbreak in humans, known as "swine flu", is due to a new strain of influenza A virus subtype H1N1 that contained genes most closely related to swine influenza.The origin of this new strain is unknown. However, the World Organization for Animal Health (OIE) reports that this strain has not been isolated in pigs. This strain can be transmitted from human to human, and causes the normal symptoms of influenza.

Pigs can become infected with human influenza, and this appears to have happened during the 1918 flu pandemic and the 2009 flu outbreak.