According to the CDC, swine flu or swine influenza, is a respiratory disease in pigs caused by type A influenza virus belonging to the Orthomyxoviridae family. Apart from type A swine flu, there is also the type C swine flu virus, though this strain is rare.

The subtypes of the influenza A virus that cause swine flu are H1N1, H1N2, H3N1, H3N2, and also H2N3. The three most commonly seen strains are H1N1, H1N2, and H3N2. A swine flu outbreak of the kind we have witnessed recently is not common among humans, though it is quite common among pigs. Among people, swine flu occurs as a result of contact with pigs, usually at pig farms.

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