The plague might sound like an ancient medieval problem but it’s real. Now a third cat in the past six months has tested positive for the plague, leading authorities to wonder how these cats are getting the disease.

“Plague is a serious bacterial infection that can be deadly for pets and people if not treated as soon as possible with antibiotics,” Alexia Harrist, a state health officer and state epidemiologist with Wyoming Department of Health, said in a statement. “The disease can be passed to humans from ill animals and by fleas coming from infected animals. We are letting people know of the potential threat in the cat’s home area as well as across the state.”

So if you live in Wyoming, keep your cat indoors and give it regular checkups. The best way to deal with any disease is to prevent it from spreading in the first place.

To read about the latest Wyoming cat infected with the plague, click here.