First detected in January 2004 among racing greyhounds in South Florida, H3N8 had caused outbreaks at 20 tracks in 11 states by spring of 2005.
So far, two different strains of canine influenza virus have been identified: H3N8 and H3N2.
First detected in January 2004 among racing greyhounds in South Florida, H3N8 had caused outbreaks at 20 tracks in 11 states by spring of 2005. H3N8 was originally an equine influenza strain that “jumped species” and is now well established among dogs. The virus has now been seen in 30 states and is considered endemic to Colorado, Florida, New York and Pennsylvania.
H3N2, originally an avian flu, was first found in dogs in 2007 in South Korea. The virus was first identified in the United States in the Chicago area, and by April 2015 an estimated 1,000 dogs had been affected in Illinois and nearby areas. By July, H3N2 was found in multiple states, including Alabama, California, Texas, Georgia, North Carolina, Pennsylvania, Ohio, Massachusetts, New York, Wisconsin, Michigan, New Jersey, Iowa and Indiana. How the virus reached the United States is not known.
Both strains of influenza pass readily from dog to dog via nasal secretions. This can happen through direct nose-to-nose contact, by way of airborne secretions and through contact with shared objects, such as food and water
Both strains of influenza pass readily from dog to dog via nasal
and kennel surfaces. People can also transfer the virus between dogs on their skin and clothes. According to the American Veterinary Medical Association (AVMA), flu virus can survive on surfaces for 48 hours, on clothing for 24 hours and on hands for 12 hours. It spreads most readily among dogs kept in close quarters, such as kennels, shelters, daycare centers and boarding facilities.
Neither H3N2 nor H3N8 causes illness in people, but horse owners ought to be aware of the possibility of one type of cross-species infection: The strain of H3N8 that causes equine influenza may also infect dogs. “So if your horse sneezes on your friendly dog, the dog can get ill,” Dubovi says. “But that strain of the virus doesn’t transfer on to other dogs. And the canine H3N8 does not go from dogs back to horses.”
H3N2 is not known to affect horses, but it can cause respiratory illness in cats. “If you have dogs and cats in your home, and your dog gets sick, it could spread to your cats,” says Dubovi.
When a dog is exposed to canine influenza, the infection incubates for two to four days before signs of illness appear. During this time, he will shed large amounts of the virus---in other words, dogs may be contagious before they get sick. They may continue shedding the virus for up to three weeks after infection.
The viruses cause inflammation of the lining of the respiratory tract, potentially from the dog’s nose all the way to the bronchioles in the
The same strain that causes equine flu may also infect dogs. “So if your horse sneezes on your friendly dog, the dog can get ill,” says Edward Dubovi, PhD.