Canine Influenza - H3N8; H3N2

Key Points about Canine Influenza

  • Dog flu is a disease of dogs. No human infections with canine influenza have ever been reported.
  • There are two different influenza A dog flu viruses: an H3N8 virus and an H3N2 virus.
    • Canine influenza H3N8 virus has been known to exist for more than 40 years.
      • H3N8 originated in horses.
      • H3N8 first recognized in dogs in 2004.

    • Canine influenza H3N2 is an avian flu virus that adapted to infect dogs.
      • Canine H3N2 is different from human seasonal H3N2 viruses.
      • Canine H3N2 virus first detected in dogs in South Korea.
      • Detected in U.S. in April 2015.
      • It is not known how canine H3N2 virus was introduced into the United States.
  •  The signs of this illness in dogs are cough, runny nose, and fever; but not all dogs will show signs of illness.
    • The severity of illness dogs can range from no signs to severe illness resulting in pneumonia.
    • Most dogs recover in two to three weeks.
    • The percentage that dies is less than 10 percent.

  • Nearly all dogs are susceptible to infection.
    • Dogs frequently or regularly exposed to other dogs – for example, at boarding or day care facilities, dog parks, grooming salons, or social events with other dogs present – are at greater risk of coming into contact with the virus.
    • Canine flu can spread to other dogs by:
      • direct contact with aerosolized respiratory secretions (coughing and sneezing) from infected dogs.
      • uninfected dogs coming into contact with contaminated objects.
      • moving contaminated objects or materials between infected and uninfected dogs.

  • Dog owners whose dogs are coughing or showing other signs of respiratory disease should not expose their dog to other dogs, and should contact their veterinarian.

  • A vaccine to protect dogs from influenza A H3N8 has been available in the US since 2009. 
    • It is not known if this vaccine will offer protection against the H3N2 dog flu virus seen recently.

 For more information, visit or