Swine influenza (also swine flu) refers to influenza caused by any
strain of the influenza virus endemic in pigs (swine). Strains endemic
in swine are called swine influenza virus (SIV).Of the three genera of
human flu, two are endemic also in swine: Influenzavirus A is common
and Influenzavirus C is rare. Influenzavirus B has not been reported
in swine. Within Influenzavirus A and Influenzavirus C, the strains
endemic to swine and humans are largely distinct.
Swine Flu
http://bioisolutions.blogspot.com/2009/04/swine-flu-animation.html