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What is Canine Influenza?

By Colleen Williams and medically reviewed by Sarah Wallace DVM
December 17, 2018 • 3 min. read
dog flu

Also known as “dog flu,” canine influenza is a contagious respiratory disease that can be found all over the United States. This disease is caused by type-A influenza virus, meaning these viruses are capable of causing seasonal epidemics in dogs. Canine Influenza is currently present in two strains: one is H3N8 virus and the other is an H3N2 virus. The CDC reports that “canine influenza A(H3N2) viruses are different from seasonal influenza A(H3N2) viruses that spread annually in people.” Since it is easily spread, a rising number of dog parents are dealing with the virus every day.

The Origin of Canine Influenza

The two different flu strains (H3N8 and H3N2) have different origins:

  • The H3N8 virus was discovered in 2000 in horses and by 2004, the virus was detected for the first time in dogs. It’s said that the strain transmitted to racing greyhounds were competing on the same track as infected horses.
  • The H3N2 influenza virus was first discovered in 2005 in China and South Korea. Originally found in birds, this strain of A influenza virus was found in dogs by 2007. In 2015 the virus found its way to the United States, and outbreaks were reported in more than 30 states.

Despite being very contagious and causing dogs to become very ill, the dog flu has a low mortality rate of only 10%. The risk is still there, but luckily most dogs are able to pull through and make a full recovery with proper treatment.

How Canine Flu is Transmitted

The influenza virus can be transmitted in several ways which contribute to the astounding number of infected dogs. Your dog can get infected by being in direct contact with a sick dog, or you personally can transmit the disease from one dog to another by petting and being in contact with both an infected dog and an uninfected dog.

Furthermore, the virus is also spread through the air and your dog can get infected just by being in the proximity of a coughing or sneezing pooch. And last, but not least, the virus can also be transmitted if a dog was in contact with a contaminated object like a food bowl, leash, or he shared a dog crate with a sick dog. Because of this, the virus can linger at places where dogs gather and play, such as dog parks, boarding facilities, and grooming facilities.

Symptoms of Canine Flu

Once infected it usually takes two days for a dog to develop first symptoms which are very similar to those in humans:

  • Coughing, sneezing
  • Nasal discharge
  • Fever
  • Loss of appetite
  • Lethargy
  • Eye discharge

For the first 5 days, both H3N8 and H3N2 strains have the same course. During that time a dog should receive proper treatment and show signs of recovery. If your dog is suffering with signs of canine influenza and they become lethargic, stop eating, or have increased breathing rate or effort, bring them to see a veterinarian right away. Some cases of canine influenza progress to pneumonia, and hospitalization for treatment and observation may be required.

Canine Flu Treatment

Treatment is similar to flu treatment in humans: keep your dog hydrated and comfortable while the immune system fights the virus. Some veterinarians do prescribe medication such as antibiotics and anti-inflammatories to make sure your dog is more comfortable and can even administer an IV with fluids to rehydrate a sick pup. If there is a secondary infection, you may need antibiotics.

Remember – your pet health insurance policy at Healthy Paws means you can pop into the veterinary hospital and have illnesses like canine flu diagnosed and treated, saving you up to 90% on bills. If your pet is past the waiting period, the flu would be a “curable” condition and would not be pre-existing.

How Long Does the Illness Last?

On the fifth day of the illness, symptoms may cease but your dog may still be contagious. The H3N8 virus stays in a dog’s system for 15 days, after which he is no longer a carrier. However, the H3N2 virus stays in a system for 25 days during which a dog can spread the disease to other pooches. So even if your dog has recently recovered from canine influenza, keep them away from other dogs for a minimum of 3 additional weeks after they are back to normal.


Did you know there are vaccines to protect dogs against both H3N8 and H3N2? Ask your vet if you should vaccinate your pup – some immune-compromised dogs may benefit from this. Otherwise, keep your pet out of flu’s way by avoiding dog parks when there is a canine flu breakout, and stick to good hygiene habits for both you and your pet.

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This content provided by Charles Hardy and author of, a site devoted to dog lovers and their companions. They are here to help pet parents take better care of our best friends just as they have always taken better care of us. 

The content is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. Always seek the advice of your veterinarian or other qualified health provider with any questions you may have regarding a medical diagnosis, condition, or treatment options.

colleen williams
By Colleen Williams

Over the past decade, Colleen has written about health, wellness, beauty, and even pets for The New York Times, The Cut, Refinery29, xoVain, Healthy Paws Pet Insurance, and Seattle Met Magazine, as well as many beauty brands. She has a BFA in Art History from the University of New Mexico and an AAS in Fashion Design from Parsons School of Design in New York.

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Sarah Wallace DVM profile photo
By Sarah Wallace DVM

Dr. Sarah Wallace is the vice president of telehealth at Galaxy Vets, based in Fort Collins, Colo. She is actively working to increase access to veterinary care, to develop more effective communication strategies to bridge the gap between veterinarian knowledge and pet parent understanding and build happy and sustainable veterinary teams. Dr. Wallace studied biology at Lafayette College in Pennsylvania and attended veterinary school at Western University of Health Sciences in California. After graduation, Dr. Wallace started working with Just Food for Dogs, an innovative pet food startup out of southern California advocating fresh, whole-food diets for dogs. She also completed a small animal rotating internship at San Francisco Veterinary Specialists - receiving one-on-one training with San Francisco's top veterinarians in internal medicine, neurology, dermatology, oncology and surgery. After working in clinical practice, Dr. Wallace joined the field of telehealth. Dr. Wallace writes and reviews blog content for Healthy Paws Pet Insurance. Dr. Sarah Wallace on LinkedIn Cardinal Veterinary Works Consulting

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