Does Your Dog Need a Flu Shot?

What is canine influenza, and what you can do to reduce your dog’s exposure.
By Sara Greenslit DVM, May 2019, Updated October 2021
Canine Influenza

As the weather gets cooler, it’s just about flu shot time—for us humans anyway. You might not have considered your dog’s risk of catching the flu, but after the most recent wave of canine influenza outbreaks in Los Angeles, it’s a good time to learn more about it. In the very large universe of microorganisms, viruses are particularly crafty. Canine influenza is highly contagious, and while most dogs recover without incident, complications can arise.

What is canine influenza?

Influenza viruses are named for the way the hemagglutinin (HA) and neuraminidase (NA) proteins combine, and canine influenza comes in two forms or strains: H3N8 and H3N2. Only 80 percent of dogs affected by canine influenza show flu-like signs, but all infected dogs can spread the infection. The fatality rate for influenza in dogs is less than 10 percent.

The H3N8 strain that first appeared in Florida in 2004 was suspected of having jumped from racehorses to Greyhounds. Then, in 2015, dogs with H3N2 were seen in Chicago; previously known to exist only in South Korea, China and Thailand, the strain is thought to have been transmitted to dogs by infected birds found in live Asian bird markets, then possibly brought to the U.S. via imported dogs.

Dog flu targets the cells in the respiratory tract, from the nose to the small airways of the lungs, and causes mild to severe inflammation; recovery takes two to three weeks. While a dog of any age or breed can contract the flu, some may be at bigger risk, particularly puppies, pregnant bitches, dogs with concurrent respiratory disease or tracheal collapse, and those on immunosuppressive medication.

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How is canine flu spread?

During the two-to four-day incubation period before dogs show any signs of illness, the Type A influenza virus that causes the dog flu, or canine influenza, can spread through such commonplace activities as being patted on the head, sharing a tennis ball or a water bowl, or a nose-to-nose greeting. And unlike those that cause human flu, the dog flu virus is active year-round. It is recommended by most vets to isolate dogs with canine influenza for 21 days to reduce the risk of transmission.

What are the symptoms of canine influenza?

If your dog shows signs of the flu, take him to your veterinarian. To reduce its spread, ask the reception staff if you should stay in the car until ready to be seen, and enter and exit by a side door if possible. Symptoms of the flu differ between dogs, so not all dogs will display all signs.

  • A soft, dry cough that persists for 10 to 21 days despite treatment.
  • Nasal congestion and/or thick nasal discharge
  • Fever
  • Lethargy
  • Poor appetite

Influenza can be mistaken for kennel cough (aka infectious tracheobronchitis). Bacteria like Bordetella and Mycoplasma and viruses such as parainfluenza, canine distemper, and canine adenovirus-2 present similarly.

Dogs with influenza often spike fevers; using a rectal thermometer, take your dog’s temperature every four to six hours to make sure it’s staying below 103°F. (Don’t forget to mark the thermometer as the dog’s!) A high-grade fever (104°F to 106°F) and increased respiratory rate and effort could mean that your dog is developing pneumonia; your vet will most likely recommend chest x-rays to screen for this.

Treatment for the flu is supportive care. Based on your dog’s exam and signs, it may include antibiotics for secondary infections, fluid therapy, nutritional support, appetite stimulants, and dog-specific fever-reducing NSAIDs. (Don’t share yours; aspirin, ibuprofen, acetaminophen, and other human NSAIDS can be toxic for dogs.) Keep your sick dog home for at least four weeks; if you have multiple dogs, even those who seem healthy should also be restricted to home base.

Should my dog get the flu vaccine?

The good news is that the flu shot is widely available. The first canine influenza vaccine was approved in 2009 and initial tests showed no side effects.

A dog’s risk of exposure to the virus increases if they spend time at a kennel; goes to daycare, a groomer, dog parks, or dog-friendly festivals; or if a human in the house works around dogs. The risk of canine influenza is similar to dogs who are at risk for kennel cough. Ask your veterinarian about yearly flu vaccines.

The flu shot may not prevent an infection, but it can reduce its severity and duration. A bivalent vaccine that offers protection against both strains is also available.

Tips for Preventing Infection of the Dog Flu

Strategies for thwarting this sneaky virus: Maintain your dog’s core vaccines (DHPP and Bordetella), which will help him avoid a secondary respiratory infection. Bring your own water to the dog park. When you come home, take your shoes off at the door and wash your hands first thing (yes, before you greet your pets; it’s also a good practice for your own health). Leave leashes and dog coats at the door as well. Canine influenza tends to survive no longer than 48 hours in the environment and can be inactivated by common cleaners, such as a 1:30 bleach-to-water solution. Fabric items that have come in contact with sick dogs should be washed in hot water with regular detergent.

Can people get the flu from dogs?

Currently, there is no data to suggest that the influenza virus is zoonotic—that it can spread from dogs to humans—but since dogs may carry other viruses that are, it makes sense for young, elderly, pregnant or immunocompromised people to avoid contact with ill animals.

While humans may not be susceptible, other animals might be. In 2016, cats in an Indiana shelter contracted canine influenza H3N2, and dog-to-cat transmission was suspected. Sick cats show signs like nasal discharge, congestion, fatigue, lip-smacking, and excess salivation. To date, no cats have died from the flu, and no vaccine is yet available for them.

So far, there is no indication that the canine flu H3N8 can be transmitted from dogs to horses, ferrets or other animal species. However, there is some proof that guinea pigs and ferrets can become infected with H3N2. Contact your veterinarian if you have more questions.

Like most infectious diseases, when it comes to dog flu, prevention is key. For both our dogs’ benefit and our own, washing our hands frequently, keeping up-to-date on vaccines and staying home when sick go a long way toward keeping those pesky flu microbes at bay.

Updated: 
October 2021
Article first appeared in The Bark, Issue 97: Spring 2019

Photo-illustration by Tim Carpenter

Sara Greenslit, DVM, CVA, is a small-animal  veterinarian and writer who lives and practices  in Madison, Wisc.