Courtesy of the Niagara Frontier Veterinary Society

The U.S. Centers for Disease Control and Prevention (CDC), notes that canine influenza (dog flu) is a contagious respiratory disease caused by two different influenza A dog flu viruses — the H3N8 virus and the H3N2 virus. The canine influenza A(H3N2) virus differs from the seasonal influenza A(H3N2) virus that affects humans. Fortunately, dog flu poses no threat to humans, but the potential for a canine virus to change and spread between people raises concern for another human pandemic.

The H3N8 virus may have originated in horses before spreading to dogs. Horse flu viruses have existed for over 40 years and were first found in racing greyhounds in the U.S. in 2004. It has now been detected in dogs across much of the U.S. The canine influenza H3N2 virus originated in birds before spreading to dogs, and transmission from infected dogs to cats has been rarely reported. Now in more than 30 states, both viruses are considered endemic.

The CDC requires that dogs be healthy to enter the U.S., and several federal agencies regulate their entry in order to protect our borders against diseases in humans that are carried by animals and animal products. While the regulations apply only to viruses that have the potential to lead to a pandemic in humans, the CDC is preparing for the unlikely possibility that canine influenza could become threatening to humans or animals other than canines.

Signs of canine flu are cough, runny nose, high fever, lethargy, eye discharge, and reduced appetite, but not all dogs have symptoms. Severity ranges from no symptoms to severe illness that can lead to pneumonia or even death, which is rare. Most dogs recover within two to three weeks. However, if a dog develops a secondary bacterial infection, it can lead to more severe illness and pneumonia.

Scientists believe canine flu spreads mainly among dogs through respiratory droplets produced during coughing and sneezing from infected dogs, or through contact with contaminated surfaces. The CDC recommends that dog owners whose dogs show signs of respiratory disease refrain from exposing their dog to other dogs or cats. They also recommend that clothing, equipment, surfaces, and hands be cleaned and disinfected after exposure to dogs with signs of respiratory disease.

Testing and vaccines for the H3N8 and H3N2 dog flu are available in the U.S., so check with your veterinarian for a recommendation. Treating canine flu requires supportive care and ensuring that your dog is hydrated and comfortable while their body mounts an immune response to the infection. Your veterinarian may also prescribe an antibiotic if a secondary bacterial infection is suspected. Most importantly, contact your veterinarian if your dog (or cat) is exhibiting symptoms of canine flu and isolate them from other animals.

The Niagara Frontier Veterinary Society consists of 75 small animal hospitals and 220 practitioners in Erie and Niagara counties. Learn more at