All About Canine Influenza

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Existing in many mammalian and avian species, influenza A viruses are masters of shapeshifting, and can quickly morph into new strains that infect different species. An emerging disease in dogs, canine influenza virus (CIV) or dog flu is recognized in two distinct strains: H3N8, a mutation or genetic variant of equine flu and H3N2, arising from avian flu in Asia.

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Both strains of canine influenza are highly infectious and almost every dog who is exposed will become infected. Characterized by flu-like symptoms ranging from mild to severe, dog flu is transmissible through direct or indirect contact. While the fatality rate is less than 10 percent, this prolific virus is nevertheless a huge concern, particularly for dogs whose lifestyle includes being around other dogs.

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Caused by an influenza A virus, canine influenza is a highly contagious respiratory infection. All dogs are susceptible to the illness with immunosuppressed puppies, elderly, and pregnant dogs at higher risk.



A vaccine is available that protects your dog from both H3N8 and H3N2. Your veterinarian will recommend it if your dog participates in events such as dog sports, dog shows, or goes to boarding and daycare facilities, grooming salons, or dog parks.

While these social butterflies may be more at risk, most dogs today lead an active social life with many restaurants, stores, and events welcoming canine family members. Even if you only walk your dog through the neighborhood, all it takes is one interaction with an infected dog or a contaminated object for your dog to contract canine influenza.


Vaccine cost

Generally, the canine flu vaccine costs $20-30 total ($10-15 per injection, and a total of 2 injections). However, be sure to ask your veterinarian first, as prices may vary by vet or by area.

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Due to the pathogen's ease of transmittal, a flu virus infection can happen in a heartbeat. Your dog can become infected through direct physical contact with an infected dog, airborne droplets of respiratory secretions from the coughing, sneezing, and barking of an infected dog, or via contact with contaminated objects such as kennels, toys, water bowls, leashes, and collars touched by infected dogs. Further, dogs may be infected by having contact with people who have been in contact with infected dogs. The virus is alive and viable on surfaces for 48 hours, clothing for 24 hours, and thrives on hands for 12 hours. To reduce the risk of transmission, cleaning and disinfecting contaminated objects is key to prevent other dogs' exposure to the virus. Likewise, people in contact with infected dogs should thoroughly wash their hands and clean their clothing to avoid spreading the virus.



Canine influenza is rarely fatal and most dogs recover in two-to-three weeks. However, due to the wildfire effect of the contagion; prompt diagnosis, isolation of the infected dog, and supportive treatment are essential.

Clinical signs of H3N8 appear in most cases two-to-three days after exposure. Signs of respiratory illness occur between two-to-eight days after an H3N2 infection. Even though some dogs do not show clinical signs, they are contagious and shed the virus during this incubation period. About 20 percent of dogs have a subclinical infection and can still shed the virus even though they do not seem ill.


Watch for the following most common clinical symptoms of a flu infection:

  • Low-grade, mild fever about 103-degrees Fahrenheit.
  • Runny nose with mucus changing from clear to viscous.
  • Lethargic and sleepy.
  • Dry cough with or without bringing up sputum.
  • Loss of appetite.


Diagnosis is rarely straightforward for dog flu. Within a day or two of the onset of clinical signs, laboratory tests include the respiratory panel, the Influenza Virus Matrix PCR test, and Canine Respiratory PCR panel. Influenza A positive samples are then diagnosed as H3N8 or H3N2. If clinical signs persist for more than seven days, an antibody test may be required.



Supportive treatment for viral diseases such as H3N8 and H3N2 include best animal care and nutrition practices. Isolation of the patient is paramount to prevent transmission to other dogs, and in the case of H3N2, cats.

Depending on the dog's condition, antibiotics are generally used to prevent secondary infection or a non-steroidal anti-inflammatory, which reduces fever. Fluid therapy is used for dehydrated dogs. In severe cases, a dog may be hospitalized or other medications prescribed.


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With the right measures, you can prevent canine influenza. Ask your vet if the canine flu vaccine is right for your dog, and keep an eye out for the most common symptoms, and you can keep your dog safe and healthy.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.