Canine Influenza

Canine Influenza

Canine Influenza, also known as “Dog Flu”, is a highly contagious upper respiratory disease caused by Influenza A virus, either the H3N2 or H3N8 strains. Both strains share many similarities. This is not the same as the Human Influenza A virus. At this time, there are no cases of it transferring to humans.

Where is it?

Historically, outbreaks of Canine Influenza have been seen in larger urban areas due to the increased use of spaces where dogs congregate such as dog parks, day cares, and boarding facilities. H3N8 was first reported in Florida in 2008 in racing Greyhounds. H3N2 was first reported in the US in 2015 in the Chicago area. Prior to that it was reported in Asia. Recently, small pockets of occurrences have been popping up in smaller communities as well.

How is it spread?

The virus is spread through aerosolized droplets (coughing or sneezing) and direct contact. The virus can live on contaminated surfaces (Examples: bowls, kennels, toys, human hands & clothing) for up to 48 hrs. Approximately 20% of infected patients can be asymptomatic (not show symptoms) but still be able to spread the virus. Whether patients are showing symptoms or not, they can spread the virus for up to 30 days.


Infected dogs can be asymptomatic. Symptoms can come on suddenly. Signs typically appear within one to five days after a dog is infected.

  • Coughing
  • Runny eyes or nose
  • Hard swallowing or throat clearing
  • Fever
  • Lethargy
  • Decreased appetite


There are many different diseases with the same symptoms, which are commonly grouped together and called “Kennel Cough”. Therefore, a definitive diagnosis cannot be made on symptoms alone. A specific test must be run to conclusively diagnose the patient with Canine Influenza. This test requires a sample to be obtained with a swab from under the eyelid and another down the throat. Unfortunately, this test is quite costly which prohibits most clients from approving it.


For most patients, no treatment is necessary. Supportive care is recommended to keep the patient hydrated and rested, allowing their immune system to fight off the virus naturally. Only when a secondary bacterial infection is suspected would antibiotics be necessary. Most patients recover within 2-3 weeks. A patient who is otherwise immunocompromised may lead to severe illness and pneumonia, which may require more aggressive treatment such as hospitalization and IV fluids. The mortality rate is very low, rough estimates suggest <1-3%.


  • Avoid contact with other dogs (boarding facilities, daycares, dog parks, meeting dogs on walks, or other events with dogs).
  • If your dog is sick, keep them away from other dogs for at least 30 days, even if symptoms resolve.
  • Wash your hands thoroughly and change your clothes, after interacting with other dogs before coming home to yours.
  • Common household disinfectants can inactivate the virus.
  • There is a vaccine for Canine Influenza. Unfortunately, it is currently unavailable (on long term back order).

Are other species at risk?

No cases of either strain have been reported to be transferred to people yet. H3N8 has not been reported in cats, but there is evidence that the H3N2 virus can be transmitted to cats. Symptoms in cats are similar to those in dogs, but milder. There have been no reported deaths in cats due to H3N2.