canine influenza virus infographic I love veterinary

This infographic was created by Abigail Fry.

Canine Influenza

Canine Influenza (the dog flu) is a contagious viral infection that affects dog, and even cats. There are two strains of the virus that can affect dogs, known as H3N8 and H3N2, which both mainly affect the respiratory system. Very similar to the flu in humans, is its ability to infect some dogs and not others. Some dogs will come in contact with canine influenza and have no signs of illness, while others will become extremely ill. No matter the strain of the virus, each is considered highly contagious.

Symptoms of Canine Influenza

While the severity of the virus can vary, the general symptoms of canine influenza include:


  • Nasal discharge
  • Coughing
  • Red eyes
  • Fever
  • Lethargy
  • Anorexia

Each dog will be affected differently by the virus due to age, overall health, and which virus in particular they were exposed to. When having a mild case of canine influenza, a dog may experience mild respiratory symptoms. These symptoms may be so mild, that they are compared to a common condition called kennel cough. The symptoms usually resolve in 10-14 days, and dogs are able to resume their normal life.

While some patients will recover quickly, others will be hit much harder by this contagious virus. Some will experience an incredibly high fever, severe lethargy, anorexia, and respiratory complication. Dogs with a severe case of influenza have a possibility of developing pneumonia, which has the potential to be deadly when not treated quickly and appropriately.

Transmission of Canine Influenza

Canine influenza is spreads through droplets or aerosols containing the contagious virus. This means that dogs can become ill with direct contact with an infected dog, or through contact with contaminated objects. Because of this, canine influenza is usually spread in kennels, groomers,  day care facilities, dog parks, and other areas that are known to have a high volume of dogs coming and going.

The dog flu is especially contagious due to its ability to last in the environment for up to 48 hours. It is even known to survive on clothing for up to 24 hours. Because of this, the virus has the potentially to spread through a population quickly.

The incubation period can be up to 5 days (period between exposure and symptoms), so it is possible for a dog to catch the flu from what appears to be a healthy dog.

How to Diagnose Canine Influenza

In most cases, a veterinarian can come to a diagnosis based on symptoms and nearby exposure. Veterinarians usually ask which areas a dog frequents, and can come to this possible conclusion if a patient spends time in areas with other dogs.

Due to the respiratory symptoms, diagnostics usually include chest X-Rays to assess the severity of the respiratory disease, as well as diagnostic blood work to test white blood cell counts. There is a specific serology test for canine influenza, but most veterinarians usually diagnose without this diagnostic.

Treatment for Canine Influenza

Treatment for canine influenza will depend entirely on the severity of each case. Minor cases may require cough suppressants, along with rest and strict isolation until the symptoms pass. More severe cases may require antibiotics, hospitalization, and even oxygen therapy in situations where pneumonia develops.

No matter the severity of the illness, it is important to practice strict isolation with any dog experiencing respiratory symptoms. Most veterinarians recommend 2-4 weeks of isolation.