Canine influenza is caused by influenza virus type A (CIV) specially, H3N8. The first recognized outbreak of canine influenza is believed to have occurred in racing greyhounds in January 2004 at a track in Florida. Actually, CIV represents a very event in adaptive evolution; the entire genome of the H3N8 equine influenza virus was transferred to dogs and the virus adapted to the canine species to emerge as a new canine-specific virus.