Over the past three weeks, police in Youngstown, Ohio have received more than a dozen calls about masked intruders sauntering onto residents’ property in broad daylight. The perpetrators are not felonious humans, but raccoons—and as Molly Reed of the local news outlet WKBN-TV reports, the critters are acting very strangely.

Residents of Youngstown have reported that the raccoons are exhibiting “zombie-like” behavior, Reed writes. One local, Robert Coggeshall, was playing outside his house with his dogs last week when a raccoon began to approach. Coggeshall ushered his pooches into the house. The raccoon followed them to the door.

“He would stand up on his hind legs, which I’ve never seen a raccoon do before, and he would show his teeth and then he would fall over backward and go into almost a comatose condition,” Coggeshall tells Reed. “He’d come out of it, walk around and then he’d do the same thing again. Get on his hind feet and show his teeth.”

Coggeshall tried to scare the raccoon away, but it seemed to have no intention of leaving. Police have been called to 14 similar situations in recent weeks, Reed reports. All of the animals, including the one that came into Coggeshall’s yard, were euthanized.

The rogue raccoons are in all likelihood gravely ill. The Ohio Department of Natural Resources has said that the raccoons probably have a viral illness known as distemper. According to the American Veterinary Medical Association (AVMA), the virus attacks animals’ respiratory, gastrointestinal and nervous systems. Symptoms begin with pus-like discharge from the eyes, coughing, fevers and lethargy. As the disease progresses to the nervous system, more severe symptoms—among them convulsions, seizures and paralysis—begin to manifest. Though some of the symptoms are similar to rabies, the diseases are not the same.

According to Marwa Eltagouri of the Washington Post, the Youngstown raccoons’ odd behavior can likely be ascribed to brain damage caused by the virus.

Distemper often affects dogs (evidence has even been seen in the remains of a 14,000-year-old puppy), but the virus can also infect wild animals, like foxes, wolves, coyotes, tigers—and raccoons. Distemper is spread through contact with bodily fluids and feces, and the AVMA cautions that “[c]anine distemper outbreaks in local raccoon populations can signal increased risk for pet dogs in the area.” Dogs are often vaccinated against the disease when they are puppies, but if an animal does contract distemper, there is no cure and it is often fatal.

In wild raccoon populations, distemper tends to run in cycles of five to seven years, Eltagouri reports. Many raccoons survive the outbreaks, and eventually the disease just dies off. But Geoff Westerfield, a wildlife biologist with the Ohio Department of Natural Resources’ Division of Wildlife, tells Reed that trapping infected raccoons and euthanizing them is the only way to keep the number of sick animals down.