Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs, resulting in nasal secretions, a barking cough, decreased appetite, and listless behaviour.

- Swine flu produces most of the same symptoms in pigs as human flu produces in people.

- Swine flu can last about one to two weeks in pigs that survive.

- Swine influenza, also called pig influenza, swine flu, hog flu and pig flu, is an infection caused by any one of several types of swine influenza viruses.

- Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) is any strain of the influenza family of viruses that is endemic in pigs.

- As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.

- Swine influenza virus was first isolated from pigs in 1930 in the U.S.
- Investigators decided the 2009 so-called "swine flu" strain, first seen in Mexico.