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Canine Influenza

Canine Influenza is highly contagious and as a dog parent, it is always important to be prepared to face any risks to your dog’s health. While most cases of Canine Influenza are not fatal, this virus can make your pup uncomfortably sick, causing him — and you — a lot of stress, and will result in time and money spent at the full service vet’s office. If you are a dog owner, you don’t need to panic about the dog flu. You should, however, familiarize yourself with the symptoms so that you know what to look for in the event of an outbreak in your area and be aware of how to best protect your pet.

What is Canine Influenza?

Canine Influenza virus, or the dog flu, is an infectious respiratory disease caused by influenza A virus, similar to the viral strains that cause influenza in people. There are two known strains of dog flu found in the United States:

  • H3N8
  • H3N2

The H3N8 strain actually originated in horses. The virus jumped from horses to dogs, becoming a canine influenza virus around 2004. The first outbreaks affected racing Greyhounds at a track in Florida. H3N2, on the other hand, originated in Asia, where scientists believe it jumped from birds to dogs. H3N2 is the virus responsible for the 2015 and 2016 outbreaks of canine influenza in the Midwest and continues to spread throughout the United States.

How is the Dog Flu Spread?

Similar to influenza in humans, the dog flu is airborne. Transmission often comes in the form of respiratory excretions spread through coughing, barking, and sneezing, where they are then inhaled by a new canine host. This disease can also spread through contaminated objects and environments, like water bowls, toys, and kennel surfaces, or through contact with people who have had direct contact with an infected dog.

Crowded areas like boarding facilities, grooming parlors, and dog parks are breeding grounds for diseases like canine influenza. The close proximity of the dogs means that a barking, coughing, or sneezing dog can easily infect canines around him. This is made more dangerous by the fact that dogs are most contagious during the incubation period before they start exhibiting symptoms (2-to-4 days from initial exposure).

Viral shedding starts to decrease after the fourth day, but dogs with H3N8 remain contagious for up to 10 days after exposure, and dogs with H3N2 remain contagious for up to 26 days. Most vets recommend isolating dogs with H3N2 for at least 21 days to reduce the risk of transmission.

Almost all dogs that come into contact with the disease will contract it, but not all dogs that become infected show symptoms of the virus. About 20-25 percent of dogs infected are asymptomatic, but these dogs can still spread the disease. If one of your canine companions catches the flu, but the other seems unaffected, remember that he could still have the virus. Talk to your full service veterinarian about quarantine procedures for all dogs in your household.

Symptoms of Canine Influenza

How do you know if your pup has dog flu? There are several symptoms all owners should be aware of. Dog flu, unlike human influenzas, is not seasonal. Keep an eye out for the following symptoms year-round:

  • Coughing (both moist and dry)
  • Sneezing
  • Nasal discharge
  • Purulent nasal discharge
  • Runny eyes
  • Fever
  • Lethargy
  • Difficulty breathing

Most cases of dog flu are mild, but severe cases do occur. In those instances, dogs develop pneumonia, difficulty breathing, and a high fever. Luckily, the mortality rate is relatively low, with less than 10 percent of dog flu cases resulting in fatalities.


If you and your dog regularly visit dog parks, kennels, or grooming facilities, it is always best to be prepared by having him vaccinated. TCAP carries a canine influenza vaccine that protects pets from both the H3N8 and H3N2 strains of Canine Influenza. The vaccine is only $20 and it is offered during TCAP’s walk-in vaccine hours. Dogs receiving the Canine Influenza vaccine for the first time will need to get it boosted 3-4 weeks after the initial vaccine, but afterwards it only needs to be boosted annually.

The best way to prevent your dog from contracting dog flu is to keep him updated on his shots and away from public places or kennels with recently reported cases. If you come into contact with a dog that you suspect has dog flu or has recently been exposed to it, wash your hands, arms, and clothing before touching your own dog. This will reduce the risk of transmission from you to your dog.

Curious about what else you can do to protect your pet? Read more about what vaccines your dog needs

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