What is canine influenza? Canine flu is a highly contagious respiratory disease. The two strains of concern are the more typical H3N8 subtype that is a mutation of equine influenza A and H3N2. H3N2 is the strain that was first identified in Chicago in the spring of 2015. It is so contagious that the Purdue Small Animal Veterinary Teaching Hospital decreased its patient load during the 2015 outbreak of H3N2 to decrease the spread of the virus. Who is at risk? Canine influenza