Canine Influenza – What You Need To Know

Canine Influenza

Canine influenza, or dog flu, is a highly contagious viral infection that affects dogs and cats through the transmission of droplets of saliva or mucus from coughing, barking and sneezing.  In May 2018, a dog flu outbreak in Brooklyn, NY infected over a hundred dogs with the H3N2 canine influenza virus.  That virus has now migrated to Connecticut with four confirmed cases in Stamford and Greenwich since the end of July 2018.

Dogs in close contact with infected dogs in places such as kennels, groomers, day care facilities and shelters are at increased risk of infection.  So too, are those who frequent dog parks, pet stores, town greens and any other places where dogs are walked or exercised.  No dog is immune.

Canine Influenza Timeline

  • 2006- 2007 – Asia (Thailand, South Korea & China)
  • March 2015 – Chicago has first confirmed case in the US
  • Q1 2016 – Indiana has first confirmed case of H3N2 in cats
  • May 2017 – Confirmed cases in Florida, Georgia, North Carolina, South Carolina, Texas, Kentucky, Tennessee, Missouri, Louisiana, and Illinois.
  • 2018 – See Map below from

How Does the Dog Flu Spread?

According to the Centers for Disease Control and, Canine influenza can also be spread from direct contact with an infected dog or cat and indirect contact through objects like food and water bowls, collars and leashes or by people that have been in contact with infected dogs. It’s critical to clean and disinfect everything that have been in contact with an infected dog to avoid exposing other dogs to the virus. Likewise, people who have been in contact with an infected dog should thoroughly wash their hands, and any exposed skin, and change their clothing to avoid spreading the virus.

Viability & Incubation

The virus can remain alive and viable as follows:

  • On surfaces for up to 48 hours
  • On clothing for 24 hours
  • On hands for 12 hours

Dog Flu has an incubation period of 1 to 5 days, with symptoms appearing 2 to 3 days after exposure, in most cases. Dogs are most contagious during the incubation period and will shed the virus even though they are not showing any signs of illness.  Dogs infected with the virus may start showing respiratory symptoms between 2 and 8 days after infection. Some dogs may show no signs of illness, but are still infected and will still shed the virus. Virtually all dogs exposed to canine influenza virus become infected as it’s a new virus and they have no natural immunity to it.

It’s important to implement biosecurity protocols and disinfection procedures at the first sign of symptoms to reduce the risk of transmitting the virus.

What to Look For

Most dogs will contract the mild form of canine influenza. The most common sign is a cough that lasts for 10 to 21 days (similar to kennel cough) despite treatment with antibiotics and cough suppressants. Dogs may have a discharge from their nose and eyes along with sneezing, lethargy and vomiting.

Senior dogs, puppies and those with a compromised immune system are at greater risk and will exhibit more severe symptoms such as signs of pneumonia, a high fever (104°F to 106°F) and will have difficulty breathing.  Deaths from this virus have been reported.

Cats infected with H3N2​ display signs of upper respiratory infection, including nasal discharge, congestion, malaise, lip smacking and excessive salivation.


Take your dog to the Vet at the first signs of illness.  Treatment, as with any virus, is mainly supportive however they may also have an underlying bacterial infection, pneumonia or dehydration which will require additional medications and care. The dog’s overall health and good nutrition will help it to mount an effective response in fighting the flu virus and most dogs will recover in 2-3 weeks.

To prevent transmission of the virus, dogs infected with canine H3N2 influenza as well as other dogs in the household or dogs who have been exposed to the virus through contact with a sick animal, should be isolated for 4 weeks.


The American Veterinary Medicine Association (AVMA) has provided the following guidelines:

“Isolation protocols should be rigorously applied for dogs showing clinical signs of respiratory disease. Dogs exposed to Canine Influenza or exhibiting respiratory symptoms should not be brought to locations where other dogs are present such as training classes, shows or events, day care, and boarding and shelter facilities until the isolation period is completed.

Sick or exposed dogs should be isolated, preferably in an area with a separate air supply. An isolation period of 4 weeks is recommended. Wear personal protective equipment (gown and gloves at a minimum) when handling ill animals to avoid contaminating clothing. Clean and disinfect all clothing (including shoes), equipment, surfaces and hands after exposure to dogs showing signs of respiratory disease. Owners whose dogs are coughing or exhibiting other signs of respiratory disease should not participate in activities with other dogs or bring their dogs to facilities where other dogs are present to avoid exposing them to the virus.”

Stay vigilant, limit exposure and take immediate action if your dog becomes ill.  And please contact us immediately at 203-641-2428 if your dog becomes ill.


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