Your dog can get sick for a number of reasons, but did you know that canine flu is one of them?

In Chicago, more than 1,000 dogs have been diagnosed with canine influenza virus (CIV). It’s likely there are unconfirmed cases of this highly contagious virus, which lab scientists from Cornell University and the University of Wisconsin have identified as a "virus closely related to Asian strains of influenza A H3N2." Because the virus hasn't been seen in North America before, the researchers believe the "outbreak in Chicago suggests a recent introduction of the H3N2 virus from Asia."

“I’ve never seen anything like this,” says Anne Cohen, DVM, an emergency and critical care specialist at the Chicago Veterinary Emergency & Specialty Center (CVESC). “For the past two weeks we’ve had fifteen cases a day. Primary care vets are seeing that and more. There have been outbreaks in other parts of the country in the past, but nothing that compares with this one.”

Related: When To Take a Sick Pet to the Vet

An easy illness to fetch

Because CIV is rare, few dogs have built up immunity to it. This means most dogs exposed to it are at risk of getting sick. What makes it so insidious is that dogs can pass the virus to one another before the earliest symptom — a dry, hacking cough, like kennel cough — shows up. Even after symptoms have subsided, a pup who’s had the flu can still be contagious. About 20 percent of dogs carry the virus and appear symptomless. That makes every dog — even those that appear healthy — a threat to your dog’s health.

People can’t get CIV, but they can spread it from one dog to another. Virginia Mann, a spokesperson for the CVESC, spritzes herself with disinfectant spray and sponges herself down with bleach wipes before and after she spends time at the center. “I put on disposable booties before I walk in,” she adds. Mann takes these safety measures to protect her own dog. The flu virus can survive on inanimate objects for 24 to 48 hours. “If I pick up the germs on my shoes and my dog smells my shoes to find out where I’ve been, he can get sick,” she says.

Symptoms and treatment

Most dogs with CIV develop relatively mild symptoms. Besides coughing, these include sneezing and nasal discharge. There’s no specific treatment for dog flu. Most dogs get better at home with rest and plenty of fluids. “The dog’s immune system will fight the disease, the same thing that happens when humans get the flu,” says Cohen.

Related: 8 Tricks For Giving Medicine To A Dog Or Cat

Only five dogs in the Chicago epidemic are known to have died, but the disease can escalate into pneumonia, which can be fatal. If a pet becomes lethargic, stops eating, develops a fever of 103 degrees F or higher, has trouble breathing “or can’t seem to manage the cough on its own,” says Cohen, see the vet immediately.

Related: Is Your Dog’s Food Making Him Sick?

Keeping canine flu on a short leash

The only way to prevent CIV from spreading is to keep an ill pet isolated from other dogs for at least ten days after symptoms subside. That means no social life for your pup if you live in an area where dog flu is going around.

“Our vets are telling people not to go to places where dogs congregate,” says Mann. “That includes dog parks — many of them in the city now have ‘enter at your own risk’ signs — doggy day care, kennels and groomers.” Three Chicago area PetSmart stores voluntarily closed their pet hotels temporarily to help stem the spread of the disease, according to news reports.

There is a CIV vaccine. It requires a booster shot two to four weeks after the first injection and takes about a week after that to become effective. Vets don’t routinely offer it, and it’s not 100 percent protective. But it will lessen symptoms and shedding of the virus. “Talk to your vet about it; it might be something you want to consider if your dog is in close proximity to other dogs, like in a daycare,” says Cohen.

Related: 2 Vaccines Your Dog Absolutely Needs, and 4 He Might

Denise Foley is a veteran health writer and a former contributing executive editor at Prevention magazine.