Dog Flu

Canine influenza, or dog flu, is a respiratory disease caused by influenza viruses that are contagious to dogs.  There are two different influenza Type A virus strains that cause flu in dogs, H3N8 and H3N2. 

What are the clinical signs of dog flu?

The virus infects the cells of the respiratory tract from the nose to the lower airways and causes an acute respiratory infection.  Clinical signs include coughing, sneezing, ocular and/or nasal discharge, anorexia, fever, and lethargy. More severely infected dogs can also develop a secondary pneumonia.  Almost all dogs that are exposed to it become infected, but only 80% of them develop clinical disease.  The other 20% may not show clinical signs, but can still shed the virus. 

How do dogs get the flu?

Canine flu is spread from dog to dog by direct contact with respiratory secretions from infected dogs.  These respiratory secretions can be aerosolized or infect objects such as toys, bowls, clothes, and bedding.  Dogs who are coughing or sneezing should not be exposed to other dogs. 

Where did canine flu viruses come from?

The H3N8 strain of canine influenza first appeared in 2004 where there was an outbreak in racing greyhounds at a track in Florida.  It is believed that the H3N8 strain mutated from a known equine influenza, and that the virus shifted from infecting horses to dogs.  H3N8 is now a dog-specific virus.  

The H3N2 strain was first detected in dogs in Asia back in 2007, and has also been known to infect some cats.  The virus was then discovered in Chicago in April 2015.  In June 2015, there was one reported case in Orange County, CA.  It is unknown how the virus came to the United States.

How is my dog diagnosed and treated?

Unfortunately, canine flu mimics many other upper respiratory diseases and cannot be diagnosed on clinical signs alone.  Testing is available to confirm infection.  The veterinarians at South Orange County Animal Hospital will discuss different testing options based on your pet’s history and clinical findings.

There is no “cure” to influenza, and therapy is aimed largely at supportive care.  Dogs are usually treated with antibiotics for secondary bacterial infections and fluid therapy.  Most dogs recover in 2-3 weeks. 

Is there a vaccine for the canine flu?

There is an approved vaccine that protects against the H3N8 strain of influenza A.  However, there is no available vaccine for H3N2. 

Can I get the flu from my dog?

At the time of this publishing, there is no evidence of transmission of canine influenza from dogs to humans.  There are also no reports of humans infected with canine influenza.  The H3N2 strain of canine influenza is genetically different from human H3N2 viruses. 





American Veterinary Medical Association.  “Canine Influenza”.  AVMA, 22 April 2015.  Web.  5            June 2015. 

Centers for Disease Control and Prevention.  “Key Facts     about Canine Influenza (Dog Flu)”.            CDC, 22 April 2015.  Web.  5 June 2015.


Updated June 12, 2015