Canine influenza virus (CIV or Dog Flu) is highly infectious.

Modes of transmission and timing of viral shedding and clinical signs contribute to the highly contagious nature of CIV.

Transmission

Canine influenza virus (CIV) is highly contagious and rapidly spread by a combination of aerosols, droplets, and direct contact with respiratory secretions or contaminated fomites.^2,23 A substantial amount of virus is found in droplets and aerosols generated during coughing or sneezing. The virus particles form suspensions that remain airborne for prolonged periods of time, after which they settle on surfaces.^2,23 There is no data on how far CIV can travel, however, it may be estimated from data regarding the spread of other viruses. For human influenza viruses, aerosol transmission has been documented at distances of over 50 feet.² Transmission of canine distemper has been observed over distances of 20 feet, even from non-coughing dogs.²¹ This aerosolization is an important factor in the rapid spread of CIV, and is likely the cause of the explosive onset of disease in many dogs over a short period of time.²

Direct dog-to-dog transmission via contact with respiratory secretions and fomite-associated transmission are two other important mechanisms of CIV spread. Influenza viruses have been shown to persist for several hours in dried mucus.⁶ They may be picked up and passed on by human hands touching an inanimate object, such as a doorknob contaminated with mucus, and then spread to other dogs. Human handling of infected dogs followed by contact with other dogs has greatly contributed to the spread of canine influenza in shelters and other settings. There have been reports of staff at animal shelters transmitting CIV to their pet dogs at home via contaminated clothing and/or shoes.² Therefore, it is critical that effective decontamination procedures are followed to minimize the spread of the virus.²