Canine Influenza (Dog Flu)


What is canine influenza?
Canine influenza—dog flu—is a newly emerging infectious disease caused by a strain of the influenza A virus known as H3N8, that causes respiratory illness just in dogs. Other strains of the influenza A virus affect birds, horses, pigs, and people.

How contagious is it?
Just like human flu, dog flu is highly contagious. And dogs have no natural immunity to this relatively new virus - every dog exposed to it will become infected. About 80% of infected dogs will show signs of infection, and those that don’t can still spread the virus to other dogs.

Since 2003, there have been many reports of flu outbreaks in veterinary clinics, kennels, and shelters. Some were traced back to one sick dog that spread the virus throughout the facility, infecting many other dogs.

What are the signs?
The most common sign of dog flu is a persistent cough. Some dogs have a soft, moist, “productive” cough, while others have a dry cough similar to canine cough—a respiratory condition caused by a number of other viruses and bacteria. This similarity can make it hard for your vet to diagnose which illness your dog has.

About 80% of dogs that show signs will have a mild flu. Signs in this case include a low-grade fever, running nose, lack of energy, loss of appetite, and a cough that can last up to a month.

How serious is it?
Usually mild, dog flu can become quite serious in about 20% of the cases, with a high fever (104°F to 106°F) and pneumonia. A small number of dogs have died from complications associated with the illness.

How is it diagnosed?
It can be difficult to diagnose dog flu. Often confused with canine cough because the signs are so similar, dog flu isn’t suspected until the illness becomes unusually severe or prolonged. Blood or nasal swab samples must be taken at the appropriate time over the course of the illness – otherwise they may not confirm dog flu. If your dog has likely been exposed to other dogs with the flu, it is reasonable to suspect that it’s more than ordinary canine cough.

Is my dog at risk for infection?
Dogs of any breed or age are at risk - but certain venues and activities can increase your dog’s risk of infection. Review the list below to see if any apply to your pet.

Does your dog:
  • Come from a shelter, rescue center, breeding kennel, or pet store?
  • Board at a kennel or go to doggie daycare?
  • Attend group training or “dog kindergarten”?
  • Visit a groomer, dog parks, or engage with other dogs on daily walks?
  • Enter dog events?
  • Come into contact with other dogs in the waiting room during visits to your veterinary clinic?
If you answered "YES" to one or more of these questions, tell your veterinarian and ask what can be done to protect your dog from canine influenza.

How does it spread?
Dog flu spreads through direct contact (kissing, licking, nuzzling), through the air (coughing or sneezing), and contaminated surfaces (like when a person with the virus on their hands or clothing then pats or holds a dog – or touches another surface, like a tabletop.)

How can I protect my dog?
A new dog flu vaccine—the first of its kind—has been approved for use in the US. Canine Influenza Vaccine, H3N8 from Intervet/Schering-Plough Animal Health has been clinically proven to significantly reduce the severity and duration of canine influenza. The initial vaccination requires 2 doses, 2–4 weeks apart, followed by annual revaccination.

If your dog is being vaccinated for Bordetella, he/she is a likely candidate for Canine Influenza Vaccine, H3N8. Your veterinarian will advise you whether this new flu shot should be added to your dog’s vaccination schedule.

Is the new vaccine safe?
The new canine influenza vaccine was proven safe and well tolerated in over 700 dogs. There were over 30 breeds ranging in age from 6 weeks to 10 years old.

Where can I find out more?
Your veterinarian is the best person to answer any further questions you have about dog flu, and you can visit these websites for more information:
To protect your pet, talk to your vet.
He or she is the best source of information regarding your pet’s health. Call your veterinarian with any questions about dog flu and the vaccine now available.


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