The Facts About Dog Flu

Now that flu season is upon us, it’s a good time to discuss dog flu. While people flu is pretty common, the good news is that dog flu is actually quite rare. Still, as a dedicated pet parent, it’s a good idea to have a working knowledge of the dog flu, especially because many conventional veterinarians may try to pressure owners into having their dog vaccinated against this viral disease, even if it is at low risk.

Canine influenza (dog flu), is a highly contagious viral infection affecting dogs (and very rarely) cats. Currently there are two strains of canine flu, H3N8 and H3N2. Influenza viruses are able to quickly mutate and give rise to new strains that can infect the same or even different species.

Clinical Signs

Dogs can have mild or severe cases, and the milder cases resemble kennel cough that may last for several weeks and occur in most infected dogs. Typically, many veterinarians describe dog flu as a “really bad case of kennel cough!” Some dogs, mainly those more severely affected, will also be lethargic, have a fever and show respiratory signs such as sneezing, have discharge from their eyes or nose, and of course, coughing. Clinical signs typically appear one to five days after exposure to the virus. Although most dogs recover without incident, deaths due to dog flu have been reported. 

Canine influenza is transmitted through droplets/aerosols containing respiratory secretions from coughing, barking and sneezing. Dogs in close contact with infected dogs in places such as kennels, groomers, day care facilities and shelters are at increased risk of infection. Canine influenza can also be spread indirectly through objects (food and water bowls, etc.) or people that have contacted infected dogs. Most dogs exposed to dog influenza virus become infected, with approximately 80 percent developing clinical signs of disease.


While flu resembles other respiratory illnesses, testing is needed to confirm the disease. At present the most reliable way to diagnose canine influenza is through blood tests taken several weeks apart. However, the virus can also be detected on swabs from the nose. Treatment must begin while awaiting lab results, as it’s generally expected that the lab tests confirm the diagnosis rather than make the initial diagnosis.


Treatment for canine flu is typically supportive, including fluid therapy and antibiotics as needed. From a holistic perspective, immune support is critical. Maintaining adequate blood levels of vitamin D3 (via lab testing) may reduce the chance of infectious, inflammatory and cancerous diseases, and is used for treatment. Vitamin C provides antioxidant and immune support. Anti-infectious and immune-supporting herbs such as Oregon grape, goldenseal, echinacea, marshmallow, astragalus, cat’s claw, ginger, lemon balm, oregano leaf and olive leaf are very good. 


Vaccination is available for both strains of dog flu. It can reduce the risk of a dog contracting canine influenza, but as in people, vaccination may not prevent an infection, yet reduce the severity and duration of illness. 

This vaccine (two initial doses given three to four weeks apart with annual revaccination if needed) can be safely administered to healthy dogs that are more than 6 weeks old. The vaccine reduces the severity of the symptoms of canine influenza, but does not prevent infection. Vaccinated pets are less likely to develop lung lesions, have reduced days of viral shedding and are also contagious for fewer days.

The canine influenza vaccine is not recommended or needed for most dogs. In general, the vaccine is intended to protect dogs at risk for exposure to the canine influenza virus, which includes those that participate in activities with other dogs or are housed in communal facilities (boarding and training facilities,) particularly where the virus is prevalent. Consulting with a veterinarian can determine the risk of exposure and whether vaccination is appropriate.


Dog flu tends to be a rare disease, moving slowly through the canine population. Supportive care, antibiotics when needed and immune-supporting supplements, including vitamin D3, ensure the best chance of cure.


Shawn Messonnier, DVM, is the owner of Paws and Claws Animal Hospital in Plano. For more information contact 972-867-8800 or visit



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