Canine Flu Shows No Signs of Slowing Down


As of October 2017, one or both strains of canine flu have been reported in 46 states.

Last week, we reported on a 3-month outbreak of feline influenza that affected 500 cats and a veterinarian last winter. It seems this year that dogs may be more at risk than cats for flu.

Also last week, Newsweek reported that canine influenza cases have been identified in Washington, California, Arizona, Colorado, Pennsylvania, and even Canada. And, a Merck Animal Health website dedicated to this emerging threat, indicates that as of October 2017, one or both strains of canine flu (H3N2 and H3N8) are present in every state except for Hawaii, Alaska, North Dakota, and Nebraska.

Dog flu is a type A influenza virus that is highly contagious among dogs and is transmitted through respiratory secretions from coughing, barking, and sneezing. The virus can remain in the environment for up to 24 hours and can also be spread indirectly through fomites—kennels, food and water bowls, collars, leashes—or through people who have been in contact with infected dogs, according to the American Veterinary Medical Association.


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Canine influenza presents as a persistent cough, fever, nasal discharge, loss of appetite, and lethargy. It is not believed that the virus can infect humans, but it can spread among animals.


The H3N8 strain of canine influenza was first identified in January 2004 in Florida after an outbreak of respiratory infection spread among racing greyhounds. This strain is believed to have originated when the equine influenza virus jumped from horses to dogs during the 1990s. Canine H3N8 influenza has since been identified in dogs in most states.

The second strain of canine influenza, H3N2, was first identified in March 2015 following an outbreak affecting more than 1000 dogs in the Chicago area. Scientists at Cornell University and the University of Wisconsin reported that the outbreak was caused by a virus closely related to Asian strains of influenza A H3N2 viruses, which have been widespread among dogs in southern China and South Korea. Last year, canine H3N2 influenza was diagnosed in dogs in Florida, Georgia, South Carolina, North Carolina, Tennessee, Kentucky, Texas, and Illinois.

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