Is zombie deer disease dangerous to humans?

How far has CWD spread? (Image: Canva)

A mysterious and fatal illness is spreading among deer populations in North America, raising concerns among scientists, hunters and the general public. Known as Zombie Deer Disease, the condition's official name is Chronic Wasting Disease (CWD)—a highly contagious and deadly neurological disorder affecting deer, elk and moose.

The disease gets its eerie nickname from the way it affects infected animals, causing them to exhibit zombie-like behaviour, including staggering, listlessness, drooling and extreme weight loss. "As the disease progresses, infected animals become disoriented—showing a lack of fear of humans and an inability to perform basic survival functions," explains Dr Jagadish Hiremath, public health expert.

With its rapid spread and no known cure, CWD has raised concerns about its potential to jump to humans, much like mad cow disease did in the past.

The incubation period for CWD can last several months to years—meaning infected animals may appear healthy for a long time before showing symptoms. Once symptoms emerge, the disease progresses rapidly, leading to death.

"Some of the most common signs include drastic weight loss (wasting), lack of coordination and staggering movements, drooling and excessive salivation, blank stare and listlessness, difficulty swallowing and excessive thirst, and loss of fear of humans," Dr Hiremath explains, adding, "These symptoms worsen over time, ultimately resulting in the animal's death."

Zombie Deer Disease is caused by prions, which are misfolded proteins that attack the brain and nervous system. Unlike bacteria or viruses, prions are virtually indestructible and can survive in the environment for years—making the disease highly persistent and difficult to control.

"Prions spread through direct contact with infected animals or indirectly through contaminated soil, food, water and even plants," Dr Hiremath notes.

Originally detected in the 1960s in Colorado, CWD has now been confirmed in at least 31 U.S. states, parts of Canada, South Korea, Norway, Sweden and Finland. The disease is spreading at an alarming rate, affecting wild and captive deer populations alike.

While there is currently no confirmed cases of CWD infecting humans, experts warn that the possibility cannot be ruled out. Citing research, Dr Hiremath says that CWD prions can infect macaque monkeys—a species closely related to humans—when they consume contaminated meat.

This has led scientists to fear that, much like mad cow disease (Bovine Spongiform Encephalopathy, or BSE), CWD could eventually cross the species barrier and pose a threat to human health.

There is no cure or vaccine for CWD, making prevention the only way to contain its spread.

• Avoid handling or consuming infected animals: Hunters should have deer tested for CWD before eating the meat. The CDC and WHO strongly advise against eating CWD-infected venison.
• Use protective gear when handling carcasses: Hunters should wear gloves and masks when field dressing or processing wild game.
• Properly dispose of infected carcasses: Infected remains should be buried deep or incinerated to prevent contamination of soil and water.
• Monitor outbreaks: Wildlife agencies conduct CWD surveillance programs to track the disease’s spread and implement control measures.

"Increased research, surveillance, and preventive measures are crucial to containing the spread and minimising risks to wildlife and possibly humans," Dr Hiremath concludes.