Canine Influenza (H3N8) was first identified in racing greyhounds in 2004 and is thought to have evolved from equine influenza virus. Over the years, the virus has spread throughout the United States, making its appearance in Pennsylvania in 2008.
Because the virus is still emerging, many dogs, having not been exposed to the virus and therefore not able to produce antibodies against it, are susceptible to infection. The virus is spread between dogs by aerosol transmission (airborne), direct contact with an infected dog or with his secretions (even if he is not showing signs), and by indirect transmission (clothing, bowls, leashes, toys, etc.). Because of these modes of transmission, dogs that are in shelters, boarding, grooming and daycare facilities, or who go to dog parks are at a higher risk of exposure to the virus.
Some dogs infected with canine influenza virus will clear the infection, showing no signs of illness or will have a self-limiting mild illness, while other infected dogs will have flu-like symptoms (runny nose, fever, lethargy, and cough); most of these dogs will recover with supportive veterinary treatment and at-home care. However, a small percentage of dogs will go on to develop pneumonia which can become quite serious, especially for very young, old or already sick dogs, as well as for the occasional young, otherwise healthy, dog; these dogs require more aggressive veterinary treatment.
For dogs at risk of infection with canine influenza virus, vaccination is recommended. Starting the vaccine requires a series of two doses, the initial and then a booster 2-3 weeks later. The vaccine is then continued with annual boosters. Currently available vaccines do not prevent infection, but rather significantly reduce the time that an infected dog will be contagious and reduce the symptoms of illness that an infected dog may develop. If you have questions regarding your own dog, schedule an appointment with one of our veterinarians at East York Veterinary Center so your dog’s risk can be assessed and, if warranted, vaccination can be started.
Canine influenza virus is thought to be of little risk to humans. There have been no documented cases of canine influenza virus spreading from a dog to a person and, to date, no known cases of human infection. So while influenza viruses have the capacity to change and practicing good personal hygiene is always recommended (e.g., washing hands, etc.), current evidence suggests that humans are not susceptible to canine influenza virus.