Canine influenza has been identified in a dog in Calgary, Alberta. It is suspected to have been acquired from dogs that participated in a dog show in the US near the end of September. As expected, H3N2 canine flu is the cause (not H5N1 avian influenza, which has been detected in a number of poultry flocks in Alberta since September). Unfortunately, the dog died. It was a higher-risk dog for more serious disease or complications because it was a brachycephalic breed (i.e. smush-nosed breed).

The canine H3N2 influenza A strain has been present in the US since 2015, but is not known to be circulating in Canada. We had a couple of outbreaks of canine H3N2 influenza in Ontario in 2018, but we were fortunately able to eradicate it, in large part because of intensive testing and good owner compliance regarding isolating affected and exposed dogs, and likely some plain old good luck.

This virus is highly transmissible in the Canadian dog population as almost no dogs have any immunity, since most have never been exposed to the virus before and very few are vaccinated against canine flu. So, it can spread very quickly. As you’d expect, places where dogs congregate, including kennels and dog parks, are higher risk for transmission. We are getting reports of other dogs with flu-like disease in Calgary and other Alberta cities. The problem is, there are many other causes of respiratory disease in dogs, and they all can look similar to flu. So, without testing, we don’t know if we are seeing an outbreak of canine flu or just normal background canine respiratory disease activity.

How severe is influenza in dogs?

It’s like influenza in people: Most dogs have a self-limiting “flu-like illness” with fever, cough, decreased appetite and general malaise. Most will recover on their own with some TLC. Some will develop secondary bacterial pneumonia. A small percentage (1-2%) will die, with the greatest risk of death being in older dogs and brachycephalics.

Can dogs be vaccinated against canine flu?

Yes and no. Yes, there are flu vaccines for dogs. However, they have been hard to get because of production issues, and there is currently no supply available in Canada. But flu vaccines are not going to stop an outbreak regardless. It takes 2 doses and a few weeks for a dog to develop protection from a vaccine, and vaccines are not great for stopping transmission – they’re designed to reduce the severity of disease. That’s useful, especially in high risk dogs, but they’re not a good control tool for this virus.

What should people do?

Step 1: Don’t panic.

Step 2: Think about your dog’s social network. The more dogs it encounters, the higher the risk it could come in contact with the virus.

Step 3: Try to reduce your dog’s canine contacts. If I was in an area where flu was present, I’d avoid dog parks and other places where dogs can meet, until the issue is sorted out. Sometimes we have to mix dogs for specific reasons, but the more we can reduce that, the better.

Step 3b: If your dog is sick, keep it away from other dogs. Dogs with flu can be infectious for a day or so before they get sick, so we can’t rely completely on this, but any dog with potential flu (or that has been exposed to a dog with flu) should be isolated from other dogs. We’ve seen dogs that are PCR-positive for over 3 weeks after infection, so isolating them for a month is ideal. However, realistically, the risk of transmission is probably limited after 10 days. So, it becomes a matter of practicality. The longer the isolation, the better, but I’d definitely isolate for at least 10 days, as an absolute minimum.

Who should be tested?

Testing dogs is often is more useful from a population standpoint. I want to know where flu is to understand transmission and risk. It can also help with isolation recommendations. However, it rarely impacts the individual dog because rarely would be do something specific for influenza. Testing is never a bad idea, but if the dog has known contact with a dog with flu and has flu-like disease, we can be pretty confident is has the flu.

If testing is done, it needs to be done in a manner that prevents more transmission. For our outbreaks, dogs were sampled in homes and parking lots as much as possible, to limit dogs going into veterinary clinics. Clinics can handle flu cases and minimize the risk of transmission to other patients (if they know there’s a potential risk), but keeping dogs out of clinics is ideal unless they need medical care or there’s a clear need for testing (and swabbing a dog for testing can still be done outside, even at a clinic).

What’s the risk to people?

Very limited. There’s no evidence that the canine H3N2 strain of influenza can infect people. We never say never, but it’s not something we are currently concerned about. The main risk is simply from having one more influenza strain in circulation in the community, because we are most concerned about mixing of strains, where an individual gets infected with more than one flu strain at the same time, and those flu strains recombine to make a new strain. If that strain can infect people but is different enough from our seasonal human influenza viruses, then we create the risk of a new, highly transmissible human flu to which no one has any immunity. Since we are at the start of human flu season, and we are expecting a fall surge in H5N1 avian flu in wild birds, and we have endemic flu in pigs (and horses), we don’t want to add yet another flu strain to the mix. If a dog got H3N2 canine flu and also got infected with human flu (as we know they sometimes do), then the dog becomes a potential “mixing vessel.” The odds of that happening are very low, but they’re not zero, so we need to take reasonable precautions to decrease the risk.

As usual, this is a fluid situation and we’re trying to get more information. Hopefully I’ll have more updates here and on twitter/X (@weese_scott) soon.

More info about canine flu can be found in the Worms & Germs Blog infosheet on H3N2 Canine Influenza and in some of our previous Worms & Germs Blog posts on influenza.