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How Dog Flu Works

Keeping Dogs Flu-free

A Missouri animal hospital encourages people to vaccinate their dogs in April 2015. The U.S. Midwest was particularly hard hit by canine influenza.
A Missouri animal hospital encourages people to vaccinate their dogs in April 2015. The U.S. Midwest was particularly hard hit by canine influenza.
© Laurie Skrivan/ZUMA Press/Corbis

The H3N8 vaccine is considered a "lifestyle vaccine" – it's mostly administered to dogs who spend time in group facilities [source: AVMA]. The vaccine won't stop a dog from contracting the flu, but it helps ensure it's the mild form and speeds up recovery. It also reduces the level of contagiousness, so it can help prevent a full-blown outbreak [sources: AVMA, VCA].

The vaccine is only for the original U.S. strain, though. As of 2015, there's no U.S.-approved vaccine for the H3N2 dog-flu virus (though there is one available in South Korea), and it's unclear whether the H3N8 vaccine will work against the new strain [sources: CDC, Iowa State].


Dr. Landolt, for one, is doubtful. "Genetically, the two strains are distinct enough that the vaccine is likely to induce less protection, if any."

Besides vaccinating high-risk dogs, the best approach is to educate yourself and be smart. Talk to your vet about prevention. If dog flu has been an issue in your area, maybe stay away from the dog park for a while. Ask the folks at doggie day care if they've seen any respiratory symptoms in their guests, and if they have, keep your dog home. Make sure any group facility has an infection-control plan in place, which involves checking for respiratory symptoms at admission, immediately isolating a dog that starts coughing, disinfecting everything that dog has come into contact with and notifying all owners of the incident [sources: Iowa State, AVMA].

It's not fool-proof. Dogs are most contagious in the first few days of infection, before symptoms even appear; they can spread the virus for up to two weeks, even after symptoms have disappeared; and about one in five dogs doesn't develop any symptoms at all [sources: VCA, Lewis]. So just because your dog's buddies aren't coughing doesn't mean they don't have the flu.

If your dog does start coughing, isolate him or her at once, and call the vet [source: ASPCA]. In general, the earlier you seek medical help, the better the prognosis [source: ASPCA].

And if it turns out to be the flu, keep your dog isolated for up to 14 days. Use a short leash on walks and cross the street if another dog is heading toward you (call to the owner "dog flu!" so she doesn't think you just hate her) [sources: Blum Animal Hospital, Chicago Tribune]. Make sure no one gets near his or her food dishes, beds and toys. And then disinfect [sources: Lewis, ASPCA].

Disinfect yourself, too. While your dog is sick, wash your hands and change your clothes before going near another dog [source: Landolt]. Humans can't catch canine influenza, but they can spread it.

Author's Note: How Dog Flu Works

Before I started researching dog flu for this assignment, I hadn't heard of the April 2015 outbreak in the Midwest (I'm writing this in May), which appears to be quite serious and now has some people crying "epidemic." I chose not to dwell on this outbreak – this article is about solid information, not a still-unfolding situation with understandably mixed reports. But since I've been writing this, I've seen daily updates, and for some reason none of them has provided a very useful context that I now find myself able to offer, so here goes: In the initial weeks of the Midwest outbreak, it seems more than 1,000 dogs came down with the flu. I wasn't really sure if that was a lot until I tracked down CIV-infection data from Cornell University (which I did include in the article and admittedly was hiding in some distant Internet nook), and according to Cornell, in the 10 years leading up to March 2015 there were a maximum of 2,300 confirmed cases of dog flu in the United States. So it seems 1,000 dogs infected in a couple of weeks is, indeed, a LOT. (Good to know, right?)

Related Articles

More Great Links


  • The American Society for the Prevention of Cruelty to Animals (ASPCA). "Canine Influenza Virus/Canine Flu." (May 11, 2015)
  • American Veterinary Medical Association (AVMA). "Canine Influenza." April 22, 2015. (May 22, 2015)
  • American Veterinary Medical Association (AVMA). "Canine Influenza FAQ." April 22, 2015. (May 15, 2015)
  • Bowen, Melinda. "Dog Smarts: Understanding Canine Influenza in Advance with Dr. Bowen." April 16, 2015. (May 22, 2015)
  • Blum Animal Hospital. "Frequently Asked Questions: 2015 Canine Influenza Outbreak." April 21, 2015. (May 27, 2015)
  • Centers for Disease Control and Prevention (CDC). "Key Facts about Canine Influenza (Dog Flu)." April 22, 2015. (May 11, 2015)
  • The Chicago Tribune. "Editorial: Canine flu outbreak means no doggie Happy Hour." April 14, 2015. (May 27, 2015)
  • Cornell University College of Veterinary Medicine. "Test Summary for Canine Influenza Virus in Dogs." March 30, 2015. (May 22, 2015)
  • Iowa State University. "Canine Influenza." The Center for Food Security and Public Health. June 2014. (May 18, 2015)
  • Landolt, Gabriele. (Email interview.) Colorado State University School of Veterinary Medicine. May 20, 2015.
  • Lewis, Tanya. "Dog Flu Outbreak: What You Need to Know." Live Science. April 17, 2015. (May 11, 2015)
  • Payungporn, Sunchai, P. Cynda Crawford, Theodore S. Kouo, Li-mei Chen, Justine Pompey, William L. Castleman, Edward J. Dubovi, Jacqueline M. Katz, and Ruben O. Donis. "Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida." Emerging Infectious Diseases (CDC). Vol. 14, No. 6. June 2008. (Accessed May 11, 2015) Available from :
  • PetMD. "Dog Flu." (May 11, 2015)
  • South Loop Animal Hospital. "CIV Epidemic Update." April 3, 2015. (May 28, 2015)