The canine flu or canine influenza virus is a highly contagious disease that causes a respiratory infection in dogs. Because canine flu is a relatively new virus, most dogs are naïve to the virus and have not built up immunity against it, so they will become infected if exposed. Although most dogs will only have a mild disease course, up to 20 percent of dogs may develop a more severe form of the infection with a high fever and pneumonia.
Canine Flu Strains
There are two major strains of the canine flu, H3N8 and H3N2. The good news is neither of these strains is that hard to kill in the environment, especially compared to parvovirus. Any disinfectant that that is effective against parvovirus will also eliminate influenza from the environment. The biggest risk is if a dog comes in direct contact with another dog that is shedding the virus.
How Long are Dogs Contagious with Canine Influenza?
When it comes to shedding periods for the two strains of canine flu, H3N8 sheds for one to four days, while H3N2 starts shedding 24 hours after exposure and then sheds for 28 days. This means dogs with H3N2 will need to be quarantined for longer periods of time.
When dogs become exposed to the infection, most of them do not show clinical signs for approximately two to four days. Similarly, the peak shedding period (when dogs are most contagious) occurs one to four days after exposure. Because the peak shedding period and the incubation period of the virus overlap, infected dogs are most contagious before they even start showing clinical signs, contributing to the rapid spread of this virus.
How Does Canine Influenza Spread?
Canine flu spreads in the same way that the human flu spreads, which is through direct contact, aerosolized respiratory secretions (created by barking and coughing) and through contact with a contaminated surface. This infection can easily spread through coughing or sneezing, plus influenza viruses have been shown to live in dried mucus for several hours.
The virus can travel up to 20 feet through the air in respiratory secretions from infected animals coughing or sneezing.
Transmission of the virus can happen wherever dogs have contact with other dogs. Dogs in shelters, rescues, dog classes, doggie daycares, boarding facilities, pet stores, or kennels are at a higher risk of obtaining the disease. They can also become infected at the groomer, dog park, veterinary clinic, or a dog show.
Dog Flu Symptoms
Although the severity of clinical signs can vary, the leading symptoms include sneezing, eye and nasal discharge and coughing. Other symptoms may include a low-grade fever, loss of appetite, and fatigue. H3N2 can lead to severe secondary pneumonia which can cause extremely sick dogs and potential fatalities.
Canine Influenza Treatment
Dogs infected with the virus should be immediately separated from other dogs to stop the virus from spreading further. Most dogs take two to four weeks to recover but, in the case of H3N2, it is important to keep them quarantined until after the shedding period of 28 days.
There is no specific cure or treatment for the virus, so dog flu treatment is focused on general supportive care and alleviating the symptoms. Treatment often involves preventing or controlling secondary bacterial infections with antibiotics while the disease runs its course and giving intravenous fluids if the dog is dehydrated.
It is important to clean and disinfect food and water bowls and equipment. For these items, stainless steel is ideal instead of plastic because scratched plastic is hard to fully disinfect. You should also regularly wash your hands and use hand sanitizer to prevent spreading the disease to other dogs.
Similar to a parvovirus outbreak, having the right disinfectant is crucial. The disinfectant needs to penetrate the virus and not just sterilize the surface. Virkon and Oxine will penetrate organic matter and kill the virus.
Using paper towels rather than cloths when wiping down hard surfaces and disinfecting clothing or wearing disposable gowns when working with the dogs is recommended.
Canine Influenza Prevention
Because there is no treatment for canine flu, preventing the infection through vaccination is key. The Nobivac Canine Flu H3N8 Vaccine is the first licensed vaccine to protect dogs against the H3N8 strain of canine influenza. To cover both strains of the canine flu, a bivalent vaccine is available to help control both canine influenza H3N8 and H3N2. If a dog is exposed to the flu, the vaccine significantly reduces the clinical signs, severity, and spread of the infection by reducing viral shedding to other dogs. Annual re-vaccination with a single dose is recommended.
Many kennels and boarding facilities strive to prevent viral diseases by keeping immunity high and virus levels low. Cleaning and disinfection is key to keeping virus numbers low in a facility. Even if the virus enters the facility, the disease spread will be limited if the dog’s immunity is higher than virus numbers.
If you have more questions on dog flu, call our Pet Care Pros at 800.786.4751.
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Written by: Marty Greer, DVM
Director of Veterinary Services
Marty Greer, Doctor of Veterinary Medicine, has 40+ years’ experience in veterinary medicine, with special interests in canine reproduction and pediatrics. She received her Doctor of Veterinary Medicine from Iowa State University in 1981. She’s served as Revival’s Director of Veterinary Services since 2019. In 2023, Dr. Greer was named the Westminster Kennel Club Veterinarian of the Year.