Canine influenza, also known as dog flu, is a highly contagious respiratory disease caused by two specific Type A influenza viruses that affects dogs. What's important to note is that dog flu does not affect people, and canine influenza A viruses are different than the seasonal flu virus spread each year among people. In comparison, there is no "flu season" for dogs. Canine influenza can infect dogs year around.
Dog flu isn't considered common, but is highly contagious and a concern especially for dogs that have contact with many other dogs. Because it's a relatively new disease, most dogs have never been exposed to it and, therefore, have no natural immunity. Virtually, 100 percent of dogs exposed will become infected. About 20 percent of infected dogs show no signs at all but can still spread the disease. The incubation period–time from exposure to signs of illness—is two to four days, and dogs may shed virus (spread the disease) for seven to 10 days.
The Origins of Dog Flu
The H3N8 virus arose in horses, while the H3N2 virus came from birds. Both now can infect dogs. This disease first appeared in dogs in South Korea and made its first appearance in the United States in 2004, primarily affecting racing greyhounds in Florida. A major outbreak arose in April 2015 in Chicago affecting shelter dogs and others. Today, the CDC reports dog flu has been identified in 30 states.
How Dogs Catch the Flu
Dog flu is spread from infected dogs to other dogs by direct contact or nasal secretions from barks, coughs, or sneezes. Contact with contaminated surfaces, food bowls, toys, and collars can also spread the disease. People who pet a contagious pet can spread the illness to other dogs of any age or breed. That means it can be spread during visits to the dog park. Although unusual, cats also may become infected. It was reported that a group of cats in an Indiana shelter became infected with H3N2 in early 2016, transmitted from infected dogs.
The Signs of Dog Flu
Eighty percent of dogs develop flu-like symptoms. Dogs develop a honking, gagging cough (similar to the more benign "kennel cough") that lasts for up to three weeks. Dogs also have a thick nasal discharge, and a spiking fever of 104-105 degrees. Other signs include eye discharge, a lack of appetite, and lethargy.
How to Treat It
As with most viral illness, treating dog flu relies on supportive care. There are anti-viral medications for people suffering with flu symptoms, but these have not been tested in pets. Your veterinarian will have the best insight into any extra-label options. Nonsteroidal anti-inflammatory drugs may be prescribed to control fever and inflammation. Medications to control coughing may be recommended, as well as fluid therapy helps counter dehydration. In cases of pneumonia, antibiotics may be recommended.
Most dogs recover in about three weeks, but some dogs develop secondary bacterial infections that lead to dangerous pneumonia. The mortality rate for canine influenza is less than 10 percent. No deaths in cats have been reported.
How to Prevent It
Veterinarians have tests available to diagnose the strain of dog flu affecting your pet. Dogs that test positive for the illness should be quarantined up to four weeks (depending on the strain of the virus) to prevent them spreading the disease. The virus lives up to 48 hours in the environment, but household cleaners kill the virus. Normal hygiene (washing hands, dog bowls, and kennel areas) can help prevent spread of the disease to your other pets, or those outside your home.
Ask your veterinarian about vaccination for canine influenza. Experts recommend the "lifestyle" vaccine only for dogs boarded in kennels, that travel to dog parks, compete in dog shows and group activities, or otherwise frequently interact other dogs.