COLORADO SPRINGS, Colo. — It’s not just flu season for people anymore.

A highly-contagious strain of canine influenza is quickly spreading across the nation, and has already infected 24 states.

Veterinarians say the outbreak started in Chicago in March, and thousands of dogs have been getting sick.

Unfortunately, for some of them, the virus has been deadly.

Symptoms are similar to the ones we get when we have the flu, like vomiting, coughing, sneezing and a fever, and it puts dogs at risk for pneumonia.

“We have not seen any [cases] yet, but we know it’s coming,” Dr. Susan Bloss at Cheyenne Mountain Animal Hospital said.

However, it’s not a matter of if we get it, but when.

“It’s supposed to be a very, very contagious virus, though it doesn’t cause a lot of deaths in a certain subset of patients, so maybe 10 to 20 percent of them are extremely sick with very high fevers and will die,” Bloss said.

She said the dog flu virus is usually the H3N8 strain, but the one that’s spreading now is being called H3N2 and it’s much stronger.

“The problem with the new strain is, some of the more recent information in the last month is that those patients can be contagious for up to three weeks. Most of our prior viruses, the contagious part is over with in three to four days,” Bloss said.

She said dogs can still spread it, even if they aren’t showing symptoms. So your dog could be around one that’s infected, and you wouldn’t even know it. And that’s worrying dog owners.

“It sounds dangerous,” Helen West said. “[My dog is] in good shape, but I come to the dog park a lot and there might be other dogs here that have the flu.”

But luckily there are things you can do to prevent it.

“We do have the vaccine available. I think it is available to all clinics at this time,” Bloss said. “So at this point, because we do have clients that take their pets to daycare, they go to the dog park regularly, in the last week we’ve started proactively vaccinating those patients.”

On top of that, Bloss said it’s not a bad idea to limit the time your dog spends with others.

“Keep them home, don’t take them to the dog park or out where there’s going to be other dogs that they don’t know,” she said. “If there is an outbreak, that will definitely be the recommendation because it’s very likely we won’t have enough vaccine to vaccinate everybody.”

But Bloss said dogs who have gotten the Bordetella vaccine don’t get as sick as others when they come in contact with the flu. So it’s important to keep your dog’s shots up to date.

Humans can’t contract the virus, but they could spread it to healthy dogs after close contact with an infected dog.

Unfortunately, once a dog gets sick, vets can’t treat the virus, only its symptoms.