Dog Flu (Canine Influenza) in Dogs

Michael Kearley, DVM
By Michael Kearley, DVM. Reviewed by Veronica Higgs, DVM on Dec. 20, 2023

In This Article


What Is Dog Flu?

Canine influenza virus (CIV), commonly referred to as “dog flu,” is a highly contagious respiratory virus that affects dogs of all ages and breeds. Although dog flu has been discovered in most of the United States, fortunately it doesn’t commonly cause death in dogs and, for many, won’t even necessitate a trip to the veterinarian.

Dog flu is caused by two different types of influenza viruses: H3N2 and H3N8. Both were originally a flu virus affecting other canine species, birds, and equines that now also affects dogs. H3N2 can affect cats as well, but neither virus has been reported to affect humans.

Symptoms of Dog Flu in Dogs

Because dog flu is a respiratory virus, your dog will experience symptoms associated with respiratory disease and common flu-like symptoms, such as:

  • Dry cough, which often persists for weeks
  • Fever
  • Nasal and eye discharge
  • Sneezing
  • Decreased appetite
  • Lethargy or decreased energy

In severe cases of dog flu, your dog may experience secondary bacterial infections, fever (higher than 103.5 F), and even pneumonia, which can be life-threatening.

Dog flu is extremely contagious to other dogs. Studies have shown that the virus can travel up to 20 feet in dogs’ respiratory droplets when they sneeze or cough. This is the primary route of infection, but dogs can also become infected with dog flu through contaminated food and water bowls, shared toys, leashes, as well as through clothing and indirectly through human contact (i.e., handling an infected dog and then touching/playing with other dogs).

The canine influenza virus can also survive in the environment for an extensive amount of time. CIV can survive on skin and hands for 12 hours, on clothing for 24 hours, and on surfaces for up to 48 hours.

Dog flu is extremely contagious to other dogs.

It takes two to four days after exposure to the virus before clinical signs develop. This is called the incubation period. Most dogs recover within two to three weeks but dogs with H3N2 should be isolated for 21 days and dogs infected with H3N8 should be isolated for at least seven days as they may still be infectious.    

Even though any dog can become infected with dog flu, dogs adopted from shelters or those that visit crowded doggy areas such as dog parks, doggy daycares, or kennels may be at increased risk.

Causes of Dog Flu in Dogs

Canine influenza belongs to the group of influenza A viruses, which are broken down into types based on their proteins hemagglutinin (H) and neuraminidase (N). Usually, they are specific to a single species, but over time—through mutations and other changes—they can affect other animals.

H3N8 and H3N2, the types of influenza viruses seen in dogs, are prime examples. The H3N8 virus was originally found in horses and discovered in the United States dog population in 2004. The H3N2 virus was first discovered in the United States in 2015 and seemed to have originated from the Asian bird population. 

Fortunately, it has yet to be shown that humans can become infected with the dog flu or vice versa.

How Veterinarians Diagnose Dog Flu in Dogs

Symptoms of dog flu will resemble many other types of respiratory infections, so it is important that your dog be tested so treatment can be directed appropriately.

For CIV, a PCR panel is often performed, where a swab is obtained from your dog’s nose, conjunctiva, or pharynx, then submitted to a laboratory and analyzed for viral DNA. Additional testing such as bloodwork and chest radiographs are often recommended to evaluate your dog’s general health and hydration status, and to look for evidence of pneumonia, which can be life-threatening and should be treated aggressively. 

Call your veterinarian prior to arrival to let them know that your dog is experiencing flu-like symptoms, as there are protocols and procedures that need to be followed to mitigate transmission to other dogs.

Treatment of Dog Flu in Dogs

Treatment of CIV in dogs is largely supportive. Keeping your dog calm, rested, and hydrated is paramount to ensuring a speedy recovery. In the hospital, this may include IV fluids, cough suppressants, and nutritional support. For cases involving secondary bacterial infection, an antibiotic such as Clavamox® or doxycycline, among others, is often prescribed. 

Infected dogs should be isolated from other dogs (and cats) at the onset of symptoms and up to 3-4 weeks. This means no dog parks, boarding, grooming, doggy daycare, and so on.

And because the virus can be transmitted from clothing, pet parents should change clothes/shoes and disinfect with hand-washing before interacting with other pets.

Recovery and Management of Dog Flu in Dogs

Fortunately, many dogs recover from dog flu uneventfully within a few weeks and have little to no lasting complications. Your dog may have a cough that lasts during this period as well. Younger or older dogs, or dogs that are immunocompromised, may experience more severe symptoms such as pneumonia and may even die from the disease. To ensure the best outcome possible, it is important to seek veterinary attention at the first sign that your dog is sick. 

Prevention of Dog Flu in Dogs

Fortunately, there is a vaccine for dogs designed to protect against both strains of CIV. Nobivac® and Zoetis® both manufacture the vaccine, which can be given to puppies as young as 7 or 8 weeks of age, with a booster three weeks later and annually after.

Side effects are rare and include symptoms associated with hypersensitivity and allergic reactions, such as vomiting, diarrhea, facial swelling, hives, and—less likely—severe anaphylactic reaction. Dogs who frequent boarding or grooming facilities, doggie daycares, dog parks, dog shows, or other competitions are at a higher risk. 

Ask your veterinarian if vaccinations for respiratory illnesses should be part of your dog’s preventative care plan. Keep in mind that vaccines may not always prevent infection but will make it less likely—and, if infected, symptoms are often milder and the course of disease shorter. 

Fortunately, the influenza virus is easily killed in the environment, often with routine household cleaners like bleach and soapy water. Wash your hands and clothing before interacting with any dogs as well as in between dogs. Images

Michael Kearley, DVM


Michael Kearley, DVM


Dr. Michael Kearley graduated from the University of Florida College of Veterinary Medicine in 2013. He graduated with a certificate in...

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