Dog Flu Threat Increases Across America


The spread of dog flu (canine influenza virus) was inevitable – and it’s now happening. H3N2, the canine influenza virus that first appeared in the Chicago area this Spring, is now in Atlanta, GA:  Asheville, NC,  in places in New Jersey and is reemerging in Chicago. Reports of flu are also in New York City and in Florida. And no doubt, there’s more to come. In addition, one cat has now been positively diagnosed. In all at least 17 states are affected to some extent – some only a few positives, others much more.

In early Spring the canine influenza virus was first identified in the Chicago area. Once veterinarians realized this upper respiratory problem was flu, they assumed it was the same dog flu – known as H3N8 – previously seen in the U.S. It turned out though that this flu is a novel virus to the U.S., somehow arriving from Southeast Asia, called H3N2.

Dr. Melissa Bourgeois, a specialist in microbiology and Senior Specialist for Drug Safety at Merck Animal Health says she’s not surprised by the spread of flu.

Though there have been fatalities associated with the canine influenza virus, it’s unclear what those numbers are. In fact, the number of sickened dogs is even unclear.  For example, in Atlanta, there have currently 150 dogs that have tested positive dogs for H3N2. “What about the dogs who never saw the veterinarian because their flu wasn’t severe, or the dogs not tested because the veterinarian didn’t suggest or the client declined?” says Chicago veterinarian Dr. Natalie Marks. “I am certain there are far more dogs with flu than the numbers suggests.”

Also, veterinarians used a clean swab that was bleached clean for testing to confirm the virus . But that bleach was sometimes killing the virus, leading to false negatives. Now, the protocol has changed. It’s another reason to believe more dogs have had the flu than reported.

The official numbers indicated hundreds of sickened dogs in Cook County. Dr. Donna Alexander, Cook County administrator for the Department of Animal and Rabies Control, says more like perhaps as many as thousands of dogs became ill in the Windy City because of the dog flu. “I wouldn’t be surprised,” Marks agrees.

Officially there were eight fatalities in Cook County, but Alexander suggests that number is also probably higher.  Bourgeois and other sources are unclear what the number of fatalities may be outside Chicago.

It’s known that in Asia H3N2 might also affect cats – and finally it has here. “The cat (that tested positive) had been recently adopted from a New York City shelter along with another unrelated cat,” says Dr. Alexis Seguin, internal medicine specialist, Medical Affairs-Molecular Diagnostics and Medical Information Integration Specialist IDEXX Laboratories, Westbrook, ME. “Both cats developed respiratory illness, but only one was tested.  The confirmed positive cat has had a full recovery, although her housemate has some continued mild chronic cough.”

Back to the numbers, at this time, about 150 dogs have tested positive for dog flu in Atlanta, but as indicated the numbers are likely higher. Rather than look at specific numbers, dog owners may be more well served by paying attention to general trends in their community – which local veterinarians will be aware of.

In Dr. Jerry Klein’s career, which exceeds three decades, he say he’s never seen anything like what happened in Chicago. “Now I know what an epidemic looks like and we were in the middle of it,” says Klein  supervising veterinarian at Chicago Veterinary Emergency & Specialty Center in Chicago  At it’s worst, at the emergency clinic in late Spring/early Summer, there were 10 to 15 sick dogs sick daily with suspected flu, even up to 20 dogs on some days, and about 100 a week. By late June, most clinics were seeing zero dog flu cases weekly, including the emergency clinic. Over the past week or a two there’s been a little ‘blip.’ The dog flu has remerged to from about one to a handful of cases in a week. Some suspect infected shelter dogs exposed to flu are spreading virus in foster homes or being adopted out and infecting others. Other experts suggest it’s a sign that eventually the dog flu could become endemic in the Chicago area, and will periodically re-emerge just a bit. “It’s obviously still out there,” Klein adds.

So, while many suggested “all clear” in the Chicago metro area – that’s not exactly the right terminology. Though certainly, the incidents have declined dramatically, and so has the risk.

Dogs who caught the H3N8 flu (the flu that previously affected dogs, and still exists) have a 20 to 25 percent chance to carry the bug but did not feel sick in any way. Those are lucky dogs, but the dogs’ owners have no way to know their dog is spreading virus. That doesn’t appear to be the case with this new strain from Southeast Asia, H3N2. It appears about a 100 percent of dogs exposed will become ill. However, researchers are still learning about H3N2.

“The good news is that most dogs recover on their own or with supportive veterinary care,” says Bourgeois.

It seems the mortality rate of the H3N2 strain is about one to three percent. “That’s very low, but not if it’s your dog,” Marks adds.

Also, dogs get sick with this new strain very quickly after exposure – within a few days. However, in those intervening few days – before symptoms are seen – this is when dogs appear to be most contagious. Then the dogs continue to spread virus intermittently for up to about 20 days, according to recent studies of shelter dogs. And that cough often associated with the dog flu can linger for weeks – even a few months – making dogs (and their sleepless owners) quite uncomfortable.

“Clearly this is not something you want your dog to get,” says Marks, “But we also don’t want to create hysteria.”

Veterinary medicine is all about risk/benefit…If you live in an area where flu doesn’t exist or just one or two dogs have been diagnosed, the risk of your dog getting the  flu is minimal while there are many benefits to allow social dogs to hang with their own kind. And if dogs are appropriately vaccinated for the flu, Bordetella and other infectious disease it’s usually quite safe for dogs to play with one another.

“However, if the dog flu is occurring where you live, keep your dogs away from other dogs,” says Marks. “Talk with your veterinarian about appropriate precautions.” Likely that means no dog parks, no visits to pet stores….and perhaps avoiding dog day care, avoid boarding, no  grooming and for now even skipping dog training classes and instead private lessons may be preferred.

As for cats, Bourgeois says the risk of infection is very low. Obviously, for indoor only cats with no exposure to dogs because there are no dogs in the family, the risk is especially low. If there are dogs sick with flu in a home, or at an animal shelter where dogs are sick and cats are nearby, the odds increase. Still, it’s important to note that only one cat has tested positive for H3N2. Of course, upper respiratory issues are not uncommon in cats and it’s conceivable some cats may have gone previously undiagnosed.

The good news is that veterinarians can now test to determine if a pet has H3N2 with accuracy. It’s really amazing how fast this happened. Of course, there was no test available prior to this spring since H3N2 didn’t exist in this country. The H3N2 test, from IDEXX, is available to every veterinarian.

Also, speak with your veterinarian about the available canine influenza virus vaccine (it’s really two vaccines, an initial shot and a booster, and it’s only for dogs). The vaccine was created for the dog flu which was discovered back in 2004, H3N8. Whether or not the vaccine can prevent or at least lesson symptoms of the virus now spreading, H3N2, is unknown, according to Bourgeois. Although many veterinarians are suggesting the vaccine for social dogs. For starters, cross protection could exist. Even if the vaccine only protects for the flu strain it was created for, protecting dogs from that strain isn’t a bad idea. Also, Bourgeois talks about how the two flu viruses could even combine, and the more vaccinated dogs in the community, the less likely that may occur.

Klein says the apparent widespread increased distribution of virus “was inevitable. We don’t live in a bubble and our pets don’t either.”

Bourgeois says watch for the following symptoms:

  • – Coughing
  • – Discharge from the nose and/or eyes
  • – Not wanting to exercise
  • – Not wanting to eat
  • Hard for dog owners to tell, but a fever is another symptom. More profoundly affected dogs may have difficulty breathing and sometimes even develop pneumonia, and that’s when the canine influenza virus may potentially become life threatening.

Both Klein and Marks were among the many veterinary heroes in Chicago, and have been nominated for the honor of American Veterinary Medical Foundation America’s Favorite Veterinarian.