Scientists have raised concerns that chronic wasting disease (CWD), also known as "zombie deer disease," could potentially spread to humans after a deer carcass in Yellowstone National Park tested positive for the highly contagious prion disease. CWD is a fatal brain disease that affects animals such as deer, elk, reindeer, and moose, and it has been found in various parts of North America, Canada, Norway, and South Korea. The disease is characterized by symptoms such as weight loss, stumbling, listlessness, and neurological issues.

Although there have been no recorded cases of CWD infecting humans, some scientists believe that the absence of a “spillover” case does not guarantee that it will not happen in the future. Dr. Cory Anderson, a program co-director at the Center for Infectious Disease Research and Policy, warns that a similar scenario to the Bovine spongiform encephalopathy (BSE) outbreak in Britain, known as mad cow disease, could occur if CWD were to infect humans. He emphasizes the importance of being prepared for the potential spread of the disease to humans, even though there are currently no known treatments or vaccines for CWD.

What is particularly worrying is that CWD is difficult to eradicate once it contaminates the environment. The prion disease can persist in dirt or on surfaces for years, and it is resistant to disinfectants, formaldehyde, radiation, and incineration. Furthermore, studies suggest that CWD may pose a risk to certain types of non-human primates, such as monkeys, that consume meat from infected animals or come into contact with their brain or body fluids.

In Wyoming, where the disease has spread across the state since the mid-1980s, CWD has been estimated to be present in 10-15% of the mule deer population near Cody, which migrates to the southeastern section of Yellowstone during the summer. The long-term effect of the disease on deer, elk, and moose in Yellowstone is uncertain, according to park officials. The Alliance for Public Wildlife estimated in 2017 that 7,000 to 15,000 CWD-infected animals were being unknowingly consumed by humans each year, with the numbers expected to increase by 20% annually.

Although a group of individuals who mistakenly ate infected meat in 2005 did not experience significant changes in health conditions, the Centers for Disease Control and Prevention (CDC) recommends that hunters have animals tested before consuming the meat, especially in areas with reported CWD cases. The CDC also advises hunters to refer to state wildlife and public health guidance regarding the testing of animals harvested from areas with CWD.

To address the growing concern, Yellowstone staff have increased collaboration and information sharing with the Wyoming Game and Fish Department and other state agencies. They are actively identifying areas within Yellowstone with an increased risk of CWD and ramping up monitoring and testing efforts from carcasses.

The discovery of chronic wasting disease in 800 samples of deer, elk, and moose across Wyoming has prompted experts to warn of a potential disaster if the disease spreads to humans. They cite the British mad cow disease outbreak as an example of how things can escalate rapidly when a spillover event occurs. The disease infects the central nervous system and causes aggressive symptoms and lack of coordination in cattle. In the UK, 4.4 million cattle were slaughtered due to the spread of the disease, and 178 human deaths were attributed to the human variant. According to US biotech company Ginkgo Bioworks, zoonotic diseases transmitted from animals to humans could cause 12 times more deaths in 2050 compared to 2020. The company attributes this potential increase to climate change and deforestation, which may lead to more frequent spillover events.

The risk of CWD spreading to humans serves as a reminder of the importance of proactive measures to prevent the transmission of prion diseases into the human food chain. With the hunting season underway, it is crucial for hunters to be aware of the potential risks and take necessary precautions to ensure the safety of the meat they consume.