Scientists are warning about the rapid spread of chronic wasting disease (CWD), a fatal and contagious neurodegenerative disorder affecting deer, elk, moose, and reindeer across the United States and other countries. As of March 2025, the disease has reached 36 US states, parts of Canada, Scandinavia, and South Korea, with experts concerned about potential spillover to humans through consumption of infected game meat.
The disease, which first appeared in free-ranging deer in Colorado and Wyoming in 1981, causes symptoms including drooling, emaciation, disorientation, vacant staring, and lack of fear of people. There is currently no vaccine or treatment available.
Epidemiologist Michael Osterholm objects to the media’s use of the term “zombie deer disease,” stating: “It trivializes what we’re facing. It leaves readers with the false impression that this is nothing more than some strange fictional menace you’d find in the plot of a sci-fi film. Animals that get infected with CWD do not come back from the dead. CWD is a deathly serious public and wildlife health issue.”
No other wildlife illness is like CWD. It is brought on by an aberrant, or misfolded, cell protein. The symptoms of CWD arise when this so-called prion interacts with regular proteins in an animal’s brain, causing those cells to misfold as well. Animals that contract the infection develop mushy brains. It has been termed “zombie deer disease” and “the disease from outer space” because of the gradual deterioration of the nervous system, which leads animals to drool, stagger, and stare blankly in the latter days of their lives. An animal may not be killed for years.
CWD is caused by prions, which can remain active in soil for years and spread through animal bodily fluids and decomposition. The US Geological Survey has found that hunted animal carcasses are often transported across state lines, potentially spreading contamination.
A January 2025 report involving 67 experts who study zoonotic diseases concluded that spillover to humans would trigger a significant crisis affecting food supply, economy, global trade, and agriculture. The report indicates that the US is unprepared to handle such an event.
While no human cases have been documented, the risk is growing as more people consume potentially infected venison. CDC surveys show that 20% of US residents have hunted deer or elk, and over 60% have eaten venison or elk meat.
The Centers for Disease Control and Prevention advises against eating meat from animals suspected of CWD infection and recommends hunters get their kills tested if taken from infected regions.
Lloyd Dorsey, a professional conservationist with the Sierra Club, expresses concern about meat safety in the Greater Yellowstone area. He has criticized Wyoming’s continued operation of feedgrounds where animals gather and disease can spread.
“Wyoming has wilfully chosen to ignore conservationists, scientists, disease experts and prominent wildlife managers who were all saying the same thing: stop the feeding,” says Dorsey.
Research tracking 1,000 adult white-tailed deer and fawns in southwest Wisconsin indicates that infected animals die at rates exceeding natural reproduction, threatening population sustainability.
The presence of healthy wild carnivores can help eliminate sick CWD-carrying animals, but states in the northern Rockies have implemented policies to reduce wolf, bear, and mountain lion populations.
Wyoming maintains nearly two dozen feedgrounds, including the federal government-operated National Elk Refuge, where over 8,000 elk gather and CWD has been detected.
Tom Roffe, former chief of animal health for the US Fish and Wildlife Service, states: “This has been a slowly expanding epidemic with a growth curve playing out on a decades scale, but now we’re seeing the deepening consequences and they could be severe. Unfortunately, what’s happening with this disease was predictable and we’re living with the consequences of some decisions that were rooted in denial.”
Experts recommend maintaining healthy landscapes without artificial feeding and allowing predators to naturally eliminate sick animals. As Lloyd Dorsey notes: “As Yellowstone has been for generations, it is the most amazing and best place to get wildlife conservation right. It would be such a shame if we continued doing something as foolish as concentrating thousands of elk and deer, making them more vulnerable to catching and spreading this catastrophic disease, when we didn’t have to.”