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Canine Influenza – What You Need to Know



What is it?

Canine influenza virus (CIV) causes respiratory symptoms similar to those experienced by humans with flu, including cough, sneezing, lethargy, fever, and discharge from the nose and eyes.  There are two known influenza viruses that can infect and spread between dogs in the United States.  The two viruses, CIV H3N8 and CIV H3N2, are detailed in the graphic below.

Canine Influenza in the United States (courtesy of Zoetis Inc.)













Canine Influenza in the United States (courtesy of Zoetis Inc.)


Is there a vaccine for Canine Influenza?

YES.  There are now vaccines available in the US for both CIV H3N2 and CIV H3N8.  Although both types of CIV are H3 viruses and share some common traits, it is important to understand that they are different viruses requiring separate vaccinations.  To date there is no information indicating that dogs vaccinated for one type will be protected for the other.


Can Canine Influenza viruses infect humans?

There have been no known cases of these influenza viruses infecting humans.


CIV Transmission

CIV is spread via aerosolized respiratory secretions and contaminated objects.  Most importantly, when dogs are infected with CIV they will go through an incubation period of approximately 2-5 days.  During this time they may appear to be healthy; however, they can be shedding virus and are capable of infecting other dogs.  Two clinical syndromes have been seen in dogs infected with the canine influenza virus – a mild form of the disease and a more severe form that is accompanied by pneumonia.

  • Mild form – Dogs suffering with the mild form of canine influenza develop a soft, moist cough that persists for 10 to 30 days.  They may also be lethargic and have reduced appetite and a fever.  Sneezing and discharge from the eyes and/or nose may also be observed.  Some dogs have a dry cough similar to the traditional "kennel cough" caused by Bordetella bronchiseptica/parainfluenza virus complex.  Dogs with the mild form of influenza may also have thick nasal discharge, which is usually caused by a secondary bacterial infection.
  • Severe form – Dogs with the severe form of canine influenza develop high fevers (104F to 106F) and have clinical signs of pneumonia, such as increased respiratory rates and effort.  Pneumonia may be due to a secondary bacterial infection.

Cats can also be infected with H3N2 canine influenza show signs of upper respiratory illness, such as runny nose, congestion, malaise, lip smacking and excessive salivation.


Are all dogs at risk of getting Canine Influenza?

Because this is still an emerging disease and dogs in the US have not been exposed to it before, almost all dogs, regardless of breed or age, lack immunity to it and are susceptible to infection if exposed to the active virus.  Virtually all dogs exposed to the virus become infected and nearly 80% show clinical signs of disease, though most exhibit the mild form.  There have been fatal cases of pneumonia resulting from infection with the canine influenza virus, but the fatality rate is low (less than 10%).  Most dogs recover in 2-3 weeks.

Canine influenze vaccines are considered "lifestyle" vaccines, meaning the decision to vaccinate is based on a dog's risk of exposure.  The "at risk" population includes dogs that are kenneled, show dogs, dogs that go to groomers/dog parks/doggie daycare or dogs that have exposure to other dogs.  If you are not sure if your dog should be vaccinated, contact us to determine whether a vaccination is needed.  If you choose to board your dog with us, we strongly recommend at least the new H3N2 Canine Influenza Vaccine be administered for all dogs.  It is a two vaccine series given three weeks apart and it takes a week after the second vaccine to acquire full immunity.


What are the clinical signs?

Clinical signs include coughing, sneezing, lethargy, fever, and discharge from the nose or eyes.  Most dogs infected with CIV will only experience a mild upper respiratory tract illness and recover within a few days.  Dogs with more severe cases of influenza are often suffering from additional viral or bacterial infections.


What should I do?

If your dog becomes ill, please call us!  Many different viruses and bacteria can cause clinical signs similar to canine influenza.  If your dog is ill, keep it away from other dogs.  Voluntary quarantine for 5-7 days will help prevent transmission of most cases of canine respiratory illness, including canine influenza.


Want more information?

The American Veterinary Medical Association has helpful resources for pet owners.  For a pet owner's guide to canine influenza, click here:  For FAQ's on canine influenza, click here:

For more technical information, you can access the Cornell University website here:

Thanks to the Cornell University College of Veterinary Medicine's Baker Institute for Animal Health for this informative graphic: