Chronic wasting disease, or CWD, is a type of prion disease, according to the Centers for Disease Control and Prevention in the United States. It’s a neurodegenerative condition that infects wildlife, including deer. It has most recently been confirmed in deer, as well as moose in Canada, after previous cases were reported in Yellowstone National Park in the United States.

No cases have yet been reported in humans, but a recent medical case report by doctors in Texas, US, on the deaths of two hunters who regularly ate meat from a population of deer infected with CWD has raised fresh questions about a link with human prion disease. Both men died of CJD, but doctors investigating the deaths were unable to prove a definitive link to CWD. They urge for the need for increased surveillance and research to establish whether the disease can cross over into humans.

The CDC estimates that in areas where the prion disease is endemic, infection rates range from 10% to 25%. In 2023, surveillance results from the Canadian province of Alberta suggest a 23% positivity rate for mule deer.

Current evidence does not show that CWD can be spread to humans when they eat the meat of an infected animal, encounter infected wildlife, or drink or touch contaminated soil or water. But researchers continue to investigate whether animal-to-human transmission is possible. “The current body of research is a mixed bag, meaning we don’t know yet,” Mullinax says.