Canine Influenza: What you need to know about Dog Flu

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by Dr. Donna Spector

With flu season in full swing, Americans are concerned about the health of their pets. Although human flu doesn’t tend to infect dogs, there is a canine influenza virus that all dog owners should know about.

Dog Flu: H3N8
The dog flu virus (Influenza A subtype H3N8) was discovered in 2004 in racing Greyhounds in Florida. The virus is highly contagious between dogs but there is no evidence it can be transmitted from dogs to humans or other species. Although the virus has only been documented in 34 states, it is likely present throughout the U.S. and is considered endemic in Florida, New York, Pennsylvania and Colorado.

Dog Flu is highly contagious and easily spread
Almost 100% of dogs will be infected after exposure to this new virus. Within 2 to 4 days, 80% will develop signs of illness and the other 20% of dogs will remain asymptomatic, although they are still capable of spreading the virus. In all cases, dogs are most contagious before they start showing signs. Similar to human flu viruses, this virus is spread by respiratory secretions and readily contaminates food and water bowls, collars, leashes and bedding. The virus can stay alive on most surfaces for 48 hours, on clothing for 24 hours and hands for 12 hours but is easily killed by common disinfectants (bleach, ammonium compounds).

What are the signs of dog flu?
Like other flu viruses, this virus causes acute respiratory infection in dogs. Most dogs develop mild respiratory infection characterized by a moist or dry cough that lasts 2 to 3 weeks despite treatment, cloudy or green nasal discharge and a low-grade fever. More severe infections are possible with pneumonia and high fever. Death has been reported in 1 to 5% of dogs who are severely affected. Unlike other flu viruses, canine influenza is not seasonal and occurs year round. Dogs with canine influenza are often misdiagnosed with kennel cough (Bordatella/parainfluenza) as the signs are usually identical. For this reason, canine influenza cannot be diagnosed only on clinical signs. The most common test used for diagnosis is a blood test which identifies antibodies to the virus as early as 7 days after symptoms start. In order to confirm infection, your veterinarian will need to take another blood sample about 2 weeks later. Other tests are available and your veterinarian may recommend a different sample from your dog.

What is the treatment for dog flu?
Similar to all viral infections, the treatment for canine influenza is supportive. Secondary bacterial infections are common and many dogs require broad-spectrum antibiotic therapy to fully resolve their signs. Most previously healthy dogs will mount an immune response and recover within 2 to 3 weeks.

How can you lessen your dog’s risk of getting the flu?
Keep your dog’s immune system as healthy as possible during the winter season (and year-round) with a healthful natural diet like Halo. Halo foods contain no artificial colors, chemicals or synthetic ingredients and therefore minimize your dog’s exposure to potentially harmful substances. Halo formulas provide fruits and vitamins which supply powerful antioxidants and immune stimulants to make your dog as strong and able to fight disease as possible. Our Daily Greens and Vitamin Mineral Mix are also excellent sources of vitamins and mineral to support immune strength. Try to limit your dog’s contact with unknown dogs and certainly avoid dogs that are showing obvious signs of respiratory illness.

What to do if your dog starts showing signs (like coughing, sneezing, runny nose)

  • Keep your dog at home, away from other dogs and dog owners. Your dog should not participate in communal dog activities or be boarded/groomed. In fact, they should be isolated from other dogs for 2 weeks to prevent spread of disease.
  • Wash your hands frequently and change your clothes before seeing another dog to reduce the risk of spread. Better yet, don’t visit with other dogs while your dog is sick.
  • Schedule an appointment with your veterinarian. There is no cure for the flu but your veterinarian can test for flu and offer supportive treatment.
  • Disinfect surfaces of your home/car that your dog has had contact with before you let other dogs into your home.

Is there a vaccine for dog flu?
Recently, the USDA approved the first canine influenza vaccine. The vaccine may not completely prevent infection but vaccinated dogs will develop less severe illness and are less likely to spread the virus to other dogs. The vaccine is not recommended for every dog—only those with an “at-risk” lifestyle. This includes dogs that are boarded or kenneled frequently, go to the groomer routinely, are housed with other dogs, or have frequent dog contact (dog park, doggy daycare, etc). Ask your veterinarian if the canine flu vaccine is right for your dog.

If your dog develops a cough or any other respiratory problem, see your veterinarian immediately for an appropriate course of treatment. You can learn more about dog flu at


dr donna spectorDonna Spector, DVM, DACVIM, is a renowned, board-certified Veterinary Internal Medicine Specialist, an active AVMA and AVHMA member, and leading speaker and writer on pet health and nutrition. She is widely recognized for her role as consulting veterinarian to HALO, Purely for Pets and her TV appearances with Halo co-owner Ellen DeGeneres. Dr. Donna performs medical, nutrition and weight loss consultations for dogs and cats through her web-based veterinary consulting service,

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