Q: Do I need to worry about the dog flu?
A: This is the season when many people get sick with the flu. Some people are surprised to learn that dogs have their own flu viruses, Influenza H3N8 and H3N2. The good news is that the dog strain is different from our human version. In fact, according to the CDC, no person has ever been diagnosed with “canine flu.”
Just like in people, the primary symptoms of flu are cough, runny nose, and fever. The clinical presentation is very similar to “kennel cough.” Over eighty percent of cases are mild, with some patients showing no noticeable symptoms at all. However, a severe form that leads to pneumonia does exist. A small number of the severely affected dogs have even died. The mortality rate is low with very young, very old, sick, or debilitated dogs more likely to experience life-threatening complications. Unlike in people, these flu viruses are not seasonal.
The H3N8 and H3N2 strains are different in their aggressiveness and in their geography, so it’s important to make a distinction. The H3N8 strain has been present in horses for over forty years. Over a decade ago, veterinary experts determined that the virus had developed the ability to spread into the canine population. Since then it has been documented sporadically in most states. A few cases pop up periodically, almost always in association with animal shelters, public dog parks, and other areas with high concentrations of dogs. Despite these relatively local cases, the virus is not moving rapidly through the general canine population.
In 2015, the newer H3N2 strain was detected in dogs in the Chicago area. This strain has proven to be more persistent with more effectively sustained transmission. H3N2 is even able to infect cats. In 2017, there was an outbreak in Georgia and Florida that began at a dog show. In those two states, over 750 dogs tested positive for the virus. Several neighboring states saw occasional cases and a smaller localized outbreak ended up settling in northern Kentucky and southern Ohio. Over 85% of positive tests for the H3N2 strain have come from the five states mentioned here. It has never been diagnosed in Virginia.
There are vaccines marketed against canine influenza. When deciding to vaccinate against any disease, the risks associated with vaccinating must be weighed against the benefits. The risks of the vaccines appear to be fairly minimal. Post-vaccine soreness at the injection site, low grade fever, or other mild symptoms are the most common side effects, although with any injection there is the possibility of systemic allergic reactions. It’s important to note that the vaccines are not labeled to prevent influenza completely, but to reduce the severity of symptoms
As far as benefits, right now Virginia pets living in a home and staying in their yard or neighborhood have a very low risk of contracting the virus. For a six-week period ending on Wednesday, January 17, a grand total of ten dogs tested positive for the H3N2 strain in the entire United States – nine in Ohio or Kentucky and one in California (note that the previous outbreaks in Illinois, Georgia, and Florida have died out). Again, it has never been detected in Virginia. Although the H3N8 virus has been detected sporadically in the state over the past decade, it has never caused a widespread outbreak.
With the current statistics, I am still not ready to recommend this vaccine for broad use at this time – although I will give it at an owner’s request, to comply with the requirements of boarding kennels, or for pets travelling to high risk areas. If there was an outbreak in Virginia, I would recommend wider inoculation (and more strictly limiting exposure).
Any dog with a cough should be promptly evaluated by a veterinarian. Any coughing dogs should be kept as isolated as possible to help prevent the spread of infectious disease. Operators of kennels, pet stores, training facilities, grooming shops, and other pet related businesses should take precautions to minimize disease transmission in their facilities.
More information on canine influenza can be found at www.cdc.gov/flu/canine and by following the links provided on that site. All of the epidemiological data in this column was obtained through Cornell University’s Canine Influenza Surveillance Network at ahdc.vet.cornell.edu/news/civchicago.cfm.