Dog Flu Spreads: How Worried Should You Be?

What you should know about canine influenza: An interview with emergency and critical care veterinarian Elizabeth Rozanski.


With an outbreak of canine influenza, or flu, making headlines and broadcast on the nightly news in 2015, people are still worried that their own dog could fall victim. It’s understandable. The virus made more than 1,000 dogs sick, traveled from Chicago all the way to Massachusetts, and killed at least five pets in the Midwest — not just in Illinois but also Wisconsin, Ohio, and Indiana. What is the risk of dog flu now? Is canine influenza still the epidemic it was in 2015? For perspective on the matter, we spoke with Tufts emergency and critical care veterinarian and member of Your Dog editorial advisory board Elizabeth Rozanski, DVM, MS, DACVECC.

Your Dog: When did dogs start getting the flu?

Dr. Rozanski: Canine influenza was actually first identified in dogs as far back as 2004, on greyhound racetracks in Florida. It was caused by a mutant strain of the flu virus that they caught from horses. Initial reports said it was a very serious disease with potentially dire consequences. Indeed, about 10 percent of dogs diagnosed with the flu went on to develop life-threatening pneumonia — most notably puppies and older dogs, whose immune systems are weaker than those of other dogs. And the illness occurred in locales around the country, not just in Florida.

That said, the disease never took off in the way veterinarians worried it would. There were Internet discussions of whole kennels of dogs dying of canine influenza, but they were not based on fact. Cases of the illness simply died down.

Your Dog: So has it come back now?

Dr. Rozanski: Not exactly. Yes, there has been a new flu outbreak, but it is from a different strain of the virus. The original strain was labeled h3n8. The strain causing the recent cases of canine flu is called h3n2. It originated in Asia and is believed to have made its way to Chicago’s O’Hare Airport via jet. Perhaps it made its way onto luggage, and from there to a dog. It spread pretty aggressively in the Chicago area. Dogs got really sick. A couple of them died, but it is not known if they were also sick with other illnesses that could have precipitated their deaths.

Since it hit Chicago it has been slowly spreading east — through Michigan and even all the way to New England. It may actually be more common than we realize. It’s hard to diagnose, and clinically, canine influenza looks like any upper respiratory infection, so it may be assumed to be a regular cold when it’s not. It’s certainly highly contagious. Because the vast majority of dogs in the U.S. have never been exposed to the virus, they have little to no immunity.

Your Dog: Does that mean people should be worried?

Dr. Rozanski: It’s true that any dog can get the disease. So yes, there’s a risk. But the initial outbreak in Chicago has died down a lot. It’s not the concern we thought. Especially if you don’t live in the Chicago area, your dog is not likely to get it. But if you move around with your pet a lot — perhaps you’re a snowbird, or make frequent trips far from home with your pet — there’s somewhat more of a chance. Consider that human disease can now move around the globe in 48 hours, and dog diseases are getting close to that in terms of their ability to spread.

Your Dog: How does the canine flu spread?

Dr. Rozanski: It spreads via respiratory droplets, either through the air or on contaminated surfaces — such as clothing or people. And the virus can live for hours.

Your Dog: Is there any way you can minimize the risk that the flu virus will spread to your own dog?

Dr. Rozanski: There’s no such thing as 100 percent risk reduction — we all, dogs included, have to go out there and live — but pay attention to the local news. The canine flu comes in pockets, relatively small geographic areas, so if you hear on TV that dogs are getting the flu in your locale, you’ll want to avoid taking your dog to dog parks for the time being or to other areas where your dog could come into close contact with lots of other dogs. You’ll want to be cautious about boarding your dog at that time, too.

Your Dog: How will you know if your dog has the flu?

Dr. Rozanski: You won’t. You’ll only know your dog is sick because the signs of the flu mimic the signs of other upper respiratory illnesses. The symptoms are similar to what we see with the flu in people: coughing, nasal and eye discharge, sneezing, fever, reduced appetite, and lethargy. If you notice any of that, take your dog to the doctor.

Your Dog: So the vet can cure it if she thinks it’s the flu?

Dr. Rozanski: No. There’s no cure for the flu. What the doctor can do, first of all, is check to see whether it is in fact influenza. The veterinary school at Cornell University has developed a test called the PCR — it’s a throat swab — to see if it’s the flu virus that’s causing the symptoms. If it is, treatment is the same as for people: time, hydration, and good old fashioned nursing care by the owner. If there’s a secondary infection like pneumonia, the vet will also put the dog on antibiotics.

Your Dog: Is pneumonia a common complication?

Dr. Rozanski: With this particular strain of the flu, about 20 percent of dogs will go on to develop potentially life-threatening complications such as pneumonia. But even at that, canine influenza is fatal in less than 10 percent of all cases.

Your Dog: That still sounds like a lot.

Dr. Rozanski: It does until you think about the fact that up to 20 percent of dogs exposed to the flu virus never even show any signs of illness. Of course, they can still shed the virus and in doing so infect other dogs.

Your Dog: Is there any way to know if your dog is a carrier?

Dr. Rozanski: No. That’s true with infectious diseases in general. It’s also what makes it hard to figure out how a dog got a disease. Add in that the length of incubation is variable, and it makes it that much harder to sort through. If your dog gets sick, the virus may have been transmitted to him several days ago. You’re not going to be able to go back in your mind and figure out how he picked up the ‘bug’.

But this isn’t something that should keep people up at night. If you stay close to what’s happening in your area and you learn there’s a breakout, just keep your dog away from other dogs for the time being, not just in parks and such but also at grooming salons, pet supply stores that allow dogs, and other places that dogs congregate.

And I would say overall that concern is good; panic, unnecessary.


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