Canine Influenza (H3N8) Virus

In 2015, a canine influenza outbreak in the Midwest was determined to have been caused not by the H3N8 strain, but by the H3N2 subtype, which has been circulating in Asian dogs. It is not known if the current H3N8 vaccine will provide protection against this new virus. H3N2 has also been known to affect cats. There have been no documented cases of H3N2 flu in Oregon to date.

Canine influenza is a flu virus, subtype H3N8, that causes respiratory infection in dogs. It is believed to have jumped species from horses and was first identified in an outbreak of respiratory illness in racing dogs in Florida in 2004.

According to the Centers for Disease Control, the first evidence of H3N8 canine influenza in companion dogs was documented in spring 2005.

Oregon Cases

There were two confirmed H3N8 cases at a humane shelter in the Salem, Oregon area in early 2013, as well as a confirmed case in Albany, Oregon in fall 2013.


Canine influenza is an airborne disease, much like kennel cough (Bordetella bronchiseptica). The virus can travel in droplets from a cough or sneeze and can be transmitted by contact with contaminated objects (for instance, a chew toy).

Practically speaking, if your dog stays at home and rarely contacts other dogs, its risk of contracting the virus is likely low. If your dog is boarded, goes to day care, or the dog park, it may be at a higher risk.

The virus is considered to be endemic in the United States.

Humans, horses, cats and other animals cannot catch the H3N8 flu virus from dogs.


The symptoms of the canine influenza virus are similar to kennel cough. Coughing is the most common symptom. Most dogs diagnosed with canine influenza experience a mild form of the disease.

They usually suffer from a persistent cough that may last for as long as three weeks and may experience a yellowish nasal discharge that can be treated effectively with antibiotics.

Dogs who experience a more serious case of canine influenza frequently have a high fever and exhibit increased respiratory rates and other indications of bacterial pneumonia. Antibiotics treat this form of the disease successfully in about 95% of the cases. The fatality rate is estimated to be between 5 and 8%, but with early diagnosis and appropriate treatment by a veterinarian, this rate can be much lower.

Call your veterinarian if your dog develops a cough, especially if it has already received the Bordetella vaccine. If your dog is coughing, do not take it out to locations where it may infect other dogs.

Be sure to tell your veterinarian if your dog has been boarded, sent to the groomer or involved in any social activities (dog park, day care, etc.) within the last month.

Remember, coughing can be indicative of a variety of significant diseases or conditions. Your veterinarian is best qualified to diagnose your dog.


After handling a sick dog, wash your hands before touching your dog. Avoid contact with dogs that appear sick.

A vaccine is available. It requires two shots, given two to four weeks apart to dogs 6 weeks and older, and can be repeated annually. It is best to discuss your dog's specific risk factors with your veterinarian to determine whether vaccination against canine influenza is appropriate for your pet.

If your dog goes to day care or if you plan to board your dog, vaccination may be recommended. You should check in advance to see if the vaccination is required at these facilities. The Bordetella vaccine does not protect dogs against canine influenza.

Published: September 30, 2009;    Updated: April 15, 2015

Filed Under: Companion Animals, Dogs

Sources: Information compiled from a variety of sources, including the Oregon Public Health Veterinarian's office and the CDC.