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Going Viral

How to protect your best friend from canine influenza

All Animals magazine, May/June 2016

by Tracy L. Scott

A strain of dog flu from Asia is now affecting pets in the U.S.

Editor's note: Since this article was first published, H3N2 has been diagnosed in a group of cats in the Midwest.

We all know the signs of flu season: Local pharmacies advertise vaccination clinics. TV news anchors track the spread of the virus across the country. Over-the-counter medicines and facial tissues fly off the shelves at supermarkets.

But until 2004, when an equine influenza virus was detected in greyhounds, many people didn’t realize that dogs, too, can catch the flu. Now a new highly contagious strain of canine influenza, known as H3N2, is making headlines.

Before you go into alarm mode, keep in mind that most dogs who contract the H3N2 virus will only suffer mild symptoms, says veterinarian Barry Kellogg, a senior adviser with the Humane Society Veterinary Medical Association. “I think influenza always carries some panic or fear with it, especially in the early stages of the outbreak,” he says. “It carries over a lot because of the concerns with the human flu, but it isn’t completely justified.”

However, he notes, H3N2 has spread to at least 29 states and infected more than 2,000 dogs, so “it’s good to be cautious until we find out what exactly is going on.”

Here’s what we know so far and what you can do to keep your dog safe.

Symptoms & Treatment

The symptoms of canine flu—fever, cough, sneezing, lethargy, runny nose and loss of appetite—mimic those of other canine complex respiratory diseases commonly referred to as Kennel Cough. While researchers have tracked the spread of the virus, no one knows exactly how many dogs have been affected. You can’t simply look at a dog who’s coughing and say it’s the flu rather than kennel cough, says Kellogg, and most veterinarians aren’t testing dogs for the flu because it’s an additional cost to owners and a diagnosis doesn’t determine treatment.

I think influenza always carries some panic or fear with it, especially in the early stages of the out-break. It carries over a lot because of the concerns with the human flu, but it isn’t completely justified.”
- Barry Kellogg, HSVMA

If an infection “persists for more than a couple of days, develops a colored discharge as opposed to clear, or is accompanied by a high fever, anorexia and significant inactivity, those are signals that a dog may need veterinary care beyond just supportive at-home care with the usual lots of liquids and rest,” Kellogg says.

As with other canine respiratory illnesses, treatment will likely include antibiotics for secondary infections. Symptoms typically go away in seven to 10 days. But in severe cases, the illness can progress to pneumonia. And as with the human flu, the young, the elderly and the immune-compromised are most at risk.

Vaccination Solution? 

Last fall, drug manufacturers began offering H3N2 vaccines, but just as with human flu shots, vaccination isn’t a guarantee against infection. “The human flu vaccine is probably effective in the vicinity of 50 percent,” says Kellogg. “The new canine one, we don’t know what percentage it will prevent, but at the least it reduces the severity and the length of time” of symptoms.

Kellogg advises owners to use their best judgment and talk with their local veterinarian when determining whether to have their pets vaccinated against H3N2. If you live in an area where the virus has been found, you should consider it. But if you’re in a region with no diagnoses and your pets are more isolated from other dogs, you may opt to skip it. “There’s always a worry of, ‘Are we over-vaccinating our animals?’ ” Kellogg says. “We don’t want to compromise their immune systems.”

View a map of the states affected by H3N2 »

Contagion Factor 

The virus is a communicable disease, so socially active dogs are most at risk of contracting it from fellow canines at dog parks, doggie daycares and other areas pets gather. Humans aren’t susceptible to the disease, but the virus can live on your clothes and hands for up to 24 hours, during which time you can transmit it to another dog.

Washing your hands and not interacting with multiple pets at one time can help prevent the flu from spreading. Shared items, such as dishes, leashes and blankets, should be laundered and disinfected.

If one of your dog’s canine buddies seems to have recovered from the flu, Kellogg says there’s reason to remain diligent. “Once a dog gets it, they may shed that virus for up to three weeks. They usually get better in 6 to 10 days, but … even though he’s better he’s contagious still.” That longer shedding period is one reason researchers believe the H3N2 virus has spread faster than some other canine flu strains.

H3N2 has been found in cats in Asia, and some worry about the spread to cats, guinea pigs and ferrets in this country. But right now in the U.S., says Kellogg, “it’s safe to say it’s in canines only.”

Traveling Bug

Veterinarians first noticed the H3N2 virus had reached the U.S. in March 2015 when Chicago experienced an outbreak. Researchers believe the virus traveled here from Asia, where the strain—previously associated with birds—has plagued dogs (and, to a lesser degree, cats) for years.

Jill Lopez, senior drug safety specialist at Merck Animal Health, is part of an H3N2 task force that helped with diagnostic testing when vets realized dogs were contracting a flu other than the strain first diagnosed in dogs here in 2004. Of the 1,000 sick dogs the task force tested in 2015, 316 were positive for H3N2. “It is highly infectious and keeps popping up in weird places,” says Lopez. “There have been lots of sick dogs in Green Bay lately.”

If you are planning to travel overseas with your dog, Adam Parascandola with Humane Society International advises that you have your pet vaccinated against H3N2. If you are bringing a dog into the country, you will want to do due diligence to ensure she is free of the flu virus (and any other communicable diseases). HSI rescuers, who have traveled to South Korea to shut down dog meat farms, follow strict protocol—involving multiple vaccinations, parasite control and a holding period—before bringing animals to the U.S., says Parascandola.

Though its arrival caught many by surprise, Kellogg says the new flu strain is no reason to panic. “I’m hoping I can dispel some of the fears,” he says. “We need to keep it in perspective.”


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