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How This 'Zombie Deer Disease' Turns Deer Into Walking Corpses—And Why There's No Cure
Chronic wasting disease might just be the most terrifying illness you've never heard of. It slowly ... [+] turns the brains of infected deer (and other cervids) into spongy, deteriorating masses, triggering bizarre behavior and, inevitably, a fatal outcome.
gettyThere's a reason zombies are so etched in our culture—and why so many movie franchises revolve around the undead. There's something viscerally unsettling about their unnatural movements and eerie moans, their insatiable hunger for flesh notwithstanding.
Thankfully, "zombie deer disease," or chronic wasting disease (CWD), only affects cervids—deer, elk, moose, and their relatives. It hasn't jumped species to infect humans, and it likely never will. But history has shown that prion diseases—like mad cow disease—are unpredictable, and chronic wasting disease is already spreading at an alarming rate among wildlife.
So what exactly is this bizarre, 100% fatal disease? And how does it turn infected animals into something eerily close to the walking dead?
'Zombie Deer Disease' Is A Textbook Case Of An Animal's Biochemistry Working Against ItAt its core, chronic wasting disease is a case of an animal's own biology betraying it. The culprits are something called prions. These are essentially "misfolded" proteins that wreak havoc by triggering a destructive domino effect in the brain.
To understand how this works, think of proteins like oil in an engine. Fresh, clean oil keeps everything running smoothly, just as properly folded proteins maintain healthy brain function. But over time, oil degrades and burns, turning into thick sludge. Cleaning out this burned oil takes effort—a lot more energy than just maintaining clean oil in the first place.
Misfolded prions work the same way. When proteins misfold, they become energetically "stuck" in that abnormal shape—just like burned oil clings to an engine, turning into a goopy, sticky mess that's difficult to clean. Unfolding and refolding them into the correct shape would take an enormous amount of energy—more than the cell can realistically provide.
As a result, these prions don't get repaired. Instead, they persist and interact with healthy proteins, forcing them to misfold as well, spreading the damage in a relentless chain reaction.
Once this process begins, there's no stopping it. These rogue prions pile up like toxic sludge, disrupting normal brain function and literally punching holes in tissue until it takes on a spongy appearance. The result? Severe neurological impairment, loss of coordination, bizarre behavior and, inevitably, death.
But the real nightmare of prion diseases isn't just how they kill—it's how they spread.
Chronic Wasting Disease Prions Are Highly Successful At Infecting New HostsAt first glance, chronic wasting disease prions might seem like a virus or bacteria—an infectious agent with a survival instinct, spreading from one host to another. But prions aren't alive. They have no DNA, no metabolism, and no biological "motivation" to infect. They are nothing more than misfolded proteins, as I mentioned earlier.
So why do they spread so aggressively? Unlike viruses or bacteria, which evolve to survive and reproduce, prions have no intentional drive—they simply follow the laws of physics and biochemistry.
Unlike traditional infectious agents, which typically spread through bodily fluids or direct contact, CWD prions can persist in an infected animal's saliva, urine, feces and even decomposing carcasses. This means an animal shedding prions doesn't need to come into direct contact with another to transmit the disease—it only needs to exist in the same surroundings.
Studies have shown that prions can remain infectious in soil for years, even binding to plant material. When another deer grazes in the same area, it unknowingly ingests the prions and becomes infected, kickstarting the entire process again.
Why There's No "Off Switch"Most diseases burn themselves out in one of two ways:
Prions don't play by these rules. There is no immune response against prions. The body doesn't recognize them as foreign invaders, so it doesn't fight back. And because prions persist in the environment long after an infected animal has died, they don't need a living host to remain a threat.
These prions are, in many ways, the perfect biological anomaly—an infectious agent that isn't alive but still manages to spread, corrupt and kill with near-perfect efficiency.
They don't need a brain, a body, or a goal. Just time—and more proteins to corrupt. And out there in the wild neither is in short supply.
What Does Chronic Wasting Disease Look Like?At first, chronic wasting disease (CWD) is almost invisible. An infected deer, elk, or moose can go years without showing a single sign that something is wrong. It moves normally, eats as usual, and blends in with the rest of the herd. But beneath the surface, its brain is already starting to unravel.
In the early stages, the symptoms are subtle. The animal might start losing weight, even though it's still eating. It may appear slightly more sluggish than usual or seem just a little off.
But as months pass, the brain and nervous system start breaking down, and the symptoms become impossible to miss.
By the time the disease reaches its peak, the infected animal is barely in control of its own body. The brain is so riddled with holes that basic functions—walking, standing, swallowing—become impossible. It shudders uncontrollably, collapses and is left helpless in a state of agony.
This is not a quick or merciful death. Unlike predators, which kill swiftly, prion diseases drag their victims toward an inevitable end—slowly, painfully, and with no possibility of recovery.
Zombie Deer Disease—A Slow But Relentless Spread With No End In SightChronic wasting disease isn't just a rare, isolated phenomenon—it's expanding, and fast. As of early 2025, the disease has been detected in wild deer, elk, and moose across 36 U.S. States and four Canadian provinces. It's also been found in captive cervid facilities in 22 states and three provinces, showing just how deeply embedded these prions have become in certain regions.
In some hotspots, however, the numbers are plain staggering. More than 50% of adult male deer in certain areas have tested positive for CWD. Among adult females, the infection rate can exceed 30%. Even on a broader scale, the numbers are troubling—some states report infection rates above 10% in their deer populations, and localized studies have found that as many as 1 in 4 animals are carrying the disease.
And once prions establish themselves in an ecosystem, they don't leave. They persist in the soil, in water sources, and on plants—long after the original infected hosts are gone. Every new animal that grazes, drinks, or simply moves through contaminated areas risks becoming the next victim in an unstoppable chain reaction.
For now, chronic wasting disease remains a wildlife crisis, but its relentless expansion raises a daunting question: What happens when an incurable, self-propagating disease is left unchecked in a world where its spread knows no limits?
It's hard not to feel pity for the deer suffering from chronic wasting disease. That same empathy is what connects us so deeply to our own pets. If you've ever wondered what truly makes your pet tick, take this free, science-backed Pet Personality Test and see how their instincts, quirks, and behaviors shape who they are.
BC Targets Two Cities In Fight To Track 'zombie Deer Disease'
Photo: Wikimedia Commons
A deer visibly showing signs of chronic wasting disease.
The province is backing the capture, killing and testing of hundreds of urban deer across two B.C. Municipalities. Their goal: find out if chronic wasting disease has spread into the city.
In a press release Friday, the Ministry of Water, Land and Resource Stewardship said the targeted removal and testing of deer would start Feb. 18 and will run until the end of the month in the Kooteney municipalities of Cranbrook and Kimberley.
Chronic wasting disease — also known as CWD or "zombie deer disease" — spreads through highly infectious prions, deformed proteins that accumulate in the animal's body.
Those prions pass into the environment through the urine or feces of infected animals, and once there, they can survive for decades, spreading the brain disease among deer, elk, moose and caribou.
Within 18 months of infection, the animals tend to show signs of weight loss, drooling and poor co-ordination. Every infected animal ends up dead.
The first B.C. Deer confirmed infected with CWD were isolated in January 2024.
The two neighbouring cities are being targeted after four of five positive samples were found over the past year were located near Cranbrook, said Jesse Zeman, executive director of the BC Wildlife Federation.
Both cities have large urban deer populations living within small home ranges and in close quarters. The ministry statement said that makes them especially prone to spreading the disease.
"We've kind of got a circle around Cranbrook," said Zeman. "We could be sitting on a major outbreak and not know. The trick now is to find out."
The ministry did not immediately respond to questions around how many deer would be targeted and how they would be killed.
But according to Zeman, learning just how prevalent CWD is in the two cities is likely to require the capture and testing of more than half of each city's deer population.
"When prevalence is really low, which it is right now, you need to drastically increase your sample size," he said. "It's going to be north of 100 deer in each community."
He said that could occur in a number of ways. The province and cities could choose to use clover traps, essentially a baited cage that traps deer so they can later be euthanized with a bolt gun. Zeman also said they could use darts to tranquilize the animals, or in extreme cases, firearms.
Whatever the method, it could prove controversial. Past attempts to cull urban deer in the communities before CWD arrived led to significant push-back from some in the community.
"It's been very controversial," said Zeman. "There are people who are very connected with the deer that live in their yard. The flip side to that is, in those cities, they're managing deer with car bumpers — running them over."
CWD was first identified in captive deer in Colorado in the 1960s. Since then it has spread to 25 American states and three Canadian provinces, in many cases, decimating local ungulate populations.
Past studies have shown primates (in particular squirrel monkeys) are susceptible to the disease. But no human has been reported ill with CWD.
That doesn't mean it couldn't happen, according to Kaylee Byers, an assistant professor at Simon Fraser University who is leading a genomic mapping project that tracks CWD in B.C.
Last fall, the researcher said that if humans were found vulnerable to zombie deer disease, it could present decades later in the same way mad cow disease (which is also spread through prions) has behaved in the past.
"We don't know if it can be passed on to people," Byers said at the time. "We just don't have a baseline."
Urban Deer A Target As B.C. Government, Cities Try To Curb Wasting Disease
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