Eating a conventional steak from a properly inspected animal carries a vanishingly small risk of transmitting mad cow disease, but the risk is not zero in theory and was not zero in practice during the BSE crisis of the 1980s and 1990s. The disease in humans is called variant Creutzfeldt-Jakob disease (vCJD), and roughly 233 cases have been confirmed worldwide, most traced to consuming contaminated beef products in the United Kingdom.1PubMed Central. Risk of variant Creutzfeldt-Jakob disease transmission by blood transfusion in Australia The reason steak specifically is low-risk comes down to where in the cow the infectious agent concentrates, and what modern regulations do to keep those parts out of the food supply.
What Mad Cow Disease Actually Does
Bovine spongiform encephalopathy, or BSE, is caused by a misfolded protein called a prion. Unlike bacteria or viruses, prions carry no DNA or RNA. They are simply normal proteins that have folded into the wrong shape, and when they come into contact with healthy versions of the same protein, they force those to misfold too. The process is slow but relentless, and once it takes hold in the brain it is always fatal. In cattle the disease is called BSE; when the same type of prion crosses into humans through contaminated food, the resulting illness is called variant Creutzfeldt-Jakob disease.2PubMed Central. Pathogenesis and Transmission of Classical and Atypical BSE in Cattle
Classical BSE is the only known prion disease in cattle that has jumped to humans.2PubMed Central. Pathogenesis and Transmission of Classical and Atypical BSE in Cattle The human form, vCJD, looks distinct from other human prion diseases under a microscope: brain tissue shows characteristic “florid plaques” surrounded by spongy holes in the cerebral cortex and cerebellum, along with severe damage to a deep brain structure called the thalamus.3PubMed. Neuropathology of variant Creutzfeldt-Jakob disease Symptoms typically start with psychiatric changes like anxiety and depression, progress to coordination problems, and eventually lead to dementia and death. There is no treatment.
Why Steak Is Different From a Burger or a Sausage
The prion that causes BSE concentrates overwhelmingly in the central nervous system: the brain, spinal cord, and the nerve-rich tissues closest to them. A steak cut from the loin, rib, or leg is skeletal muscle, which in a BSE-infected cow carries far less infectious material than what the industry calls “specified risk materials.” Those risk materials, which include the brain, spinal cord, skull, vertebral column, eyes, tonsils, and parts of the intestines, are the parts regulators have banned from the human food chain in most countries since the 1990s.
The concern was never really about someone eating a clean-cut sirloin from an infected animal. The concern was about products where nervous system tissue could get mixed in with muscle meat. During the BSE crisis, mechanically recovered meat, which uses pressure to strip every last scrap of flesh off the carcass, was a particular worry because the process could incorporate fragments of spinal cord. Studies have tested meat recovered from beef bones by different mechanical methods and found that samples from conventional systems, newer de-sinewing technology, and hand-boned cuts all tested below the detection threshold for central nervous system tissue.4PubMed. Central nervous system tissue detection in meat from advanced meat recovery systems That said, those results reflect modern, regulated processing. Before the regulations changed, cheaper processed beef products like meat pies, sausages, and fast-food patties were the likeliest vehicles for exposure, not whole cuts of steak.
The Scale of the Epidemic and Who Got Sick
The BSE epidemic in Great Britain was enormous in terms of animal cases. More than 181,000 cattle in Great Britain alone tested positive for classical BSE over the course of the outbreak.5Food Control. Classical BSE in Great Britain: Review of its epidemic, risk factors, policy and impact Millions of cattle were slaughtered as a precautionary measure. The last non-surveillance-detected BSE case in Great Britain appeared in 2012, and since 2015, only a stray case has turned up every few years through routine testing of older cattle at slaughter.
On the human side, about 229 people worldwide have been confirmed with vCJD. The overwhelming majority, around 177, were in the UK, followed by France with 27 cases. A handful occurred in Spain, Ireland, the United States, the Netherlands, Portugal, Canada, Italy, and elsewhere.6PubMed Central. Beef from the United States: Is It Safe? Consumption of BSE-contaminated beef products has been described as the primary route of human exposure, and human-to-human consumption of meat contaminated with BSE-associated prions was identified as the cause of roughly 200 of those cases.7PubMed. Prions and protein-folding diseases
Given that millions of people in the UK ate British beef during the height of the epidemic, the fact that only a few hundred developed vCJD tells you something important: either most people were not exposed to high enough doses, or there are strong individual differences in susceptibility, or both. The evidence points heavily toward genetics playing a role.
Genetics and Why Most People Did Not Get Sick
A specific spot in the gene that encodes the human prion protein, known as codon 129, comes in two common versions. You can carry methionine or valine at that position, giving you one of three possible combinations. Almost every confirmed case of vCJD has occurred in people who carry the methionine version on both copies of the gene. A genome-wide association study found that while codon 129 was the main genetic risk factor, additional spots nearby in the genome also contributed to vCJD susceptibility.8PubMed Central. Genetic risk factors for variant Creutzfeldt-Jakob disease: a genome-wide association study About 40 percent of people of European ancestry carry the double-methionine genotype, meaning the majority of the UK population during the epidemic was at least partially protected by their genetics.
This genetic filter is one reason the vCJD case count stayed in the hundreds rather than the thousands that some early models predicted. But it also raises an unsettling question: could people with other genotypes develop the disease on a much longer timeline? Research on kuru, a prion disease transmitted through ritualistic cannibalism among the Fore people of Papua New Guinea, showed that incubation periods could exceed 50 years in some individuals.9PubMed Central. A clinical study of kuru patients with long incubation periods at the end of the epidemic in Papua New Guinea That history keeps a small residual worry alive, even decades after the peak of BSE exposure.10PubMed Central. Kuru Disease: Bridging the Gap Between Prion Biology and Human Health
Cooking Does Not Make Contaminated Meat Safe
This is the part that catches most people off guard. If you grill a steak to 160°F, you kill bacteria like E. coli and salmonella. Prions are not alive, so you cannot kill them. They are proteins that have been folded into an extraordinarily stable shape, and ordinary cooking temperatures do not unfold them. Even autoclaving, which uses pressurized steam at temperatures far higher than any kitchen, does not reliably eliminate prion infectivity.
Researchers have explored extreme conditions to see what it takes. In one experiment, hot dogs spiked with scrapie prions (a related animal prion disease used as a lab model) were subjected to pressure pulses at temperatures above 120°C combined with pressures of 690 to 1,200 megapascals, conditions far beyond anything in food preparation. Even at the highest pressures, while infectivity dropped dramatically, it was reduced rather than eliminated entirely.11PubMed Central. Ultra-high-pressure inactivation of prion infectivity in processed meat: a practical method to prevent human infection Chemical decontamination with agents like guanidine hydrochloride can slash infectivity by over a hundredthousand-fold in minutes, but these are industrial-lab chemicals, not something you would apply to food.12Taylor & Francis Online (Virulence). Rapid chemical decontamination of infectious CJD and scrapie particles parallels treatments known to disrupt microbes and biofilms
The practical takeaway is straightforward: the strategy for preventing vCJD from beef is not about cooking technique. It is about keeping prion-contaminated tissues out of the food supply in the first place. Regulation, not the grill, is the safety barrier that matters.
How Regulations Protect You Today
After the BSE crisis, countries across the world overhauled their beef safety systems. The core measures are broadly similar across the US, UK, EU, Canada, Japan, and other major beef-producing nations:
- Specified risk material bans: Brain, spinal cord, skull, eyes, tonsils, distal ileum, and parts of the vertebral column from cattle above certain ages must be removed and destroyed at slaughter. These are the tissues where prion concentration is highest.
- Feed bans: The BSE epidemic was amplified by feeding rendered cattle remains back to other cattle. Ruminant-to-ruminant feed bans now prevent this recycling of prion material through the food chain.
- Surveillance testing: Cattle that die on farm, show neurological symptoms, or are older than a certain threshold are tested for BSE at slaughter. In Great Britain, active surveillance detected the steady decline in BSE cases through the 2000s and 2010s, with only one case appearing every few years by the late 2010s.13Food Control. Classical BSE in Great Britain: Review of its epidemic, risk factors, policy and impact – Section: 3.1. cBSE epidemic in Great Britain
- Import restrictions: Countries classify each other by BSE risk status (negligible, controlled, undetermined). Trade rules restrict beef imports from countries with inadequate controls.
These measures have been spectacularly effective. No new case of vCJD has been linked to beef exposure from a country with modern feed bans and specified risk material controls fully in place. The system is not perfect, and gaps in enforcement in countries with less robust veterinary infrastructure remain a theoretical concern, but the epidemic has been functionally ended by regulation.
Byproducts, Gelatin, and Hidden Exposure
Steak is not the only beef product people wonder about. Gelatin, collagen supplements, bone broth, and pharmaceutical capsules all derive from animal bones and connective tissue, which raises the question of whether prions could survive the manufacturing process. The European Food Safety Authority conducted a quantitative risk assessment modeling a worst-case scenario where all ruminant bones could be used for gelatin production and high-infectivity tissues like brain and spinal cord remained attached to the skull and vertebral column. Even under that extreme scenario, the BSE infectivity in a batch of gelatin produced according to EU processing regulations was assessed to be low.14PubMed Central. BSE risk posed by ruminant collagen and gelatine derived from bones
The reason gelatin is considered relatively safe is that the production process involves prolonged treatment with either strong acid or strong alkali, followed by high-temperature extraction. These steps degrade a large fraction of any prion material present. The specified risk material bans also apply to bones used for gelatin, so the skulls and vertebral columns most likely to harbor prions are excluded in the first place. Still, the fact that regulators continue to model worst-case scenarios and update their assessments tells you that the concern has not been entirely retired.
Atypical BSE and Whether the Story Is Really Over
Classical BSE, the type that caused the epidemic, has been brought under control. But cattle also develop rarer forms called atypical BSE, designated as H-type and L-type based on differences in the misfolded prion protein. Unlike classical BSE, these atypical forms are thought to arise spontaneously in older cattle, much like sporadic CJD occurs in humans without any known external cause.15PubMed Central. Atypical BSE: Current Knowledge and Knowledge Gaps Because they are not driven by contaminated feed, feed bans cannot prevent them.
Atypical BSE cases show up only rarely through active surveillance, typically in cattle over eight years old. Their molecular characteristics are distinct from classical BSE.16PubMed Central. Experimental H-type and L-type bovine spongiform encephalopathy in cattle: observation of two clinical syndromes and diagnostic challenges Whether atypical BSE can transmit to humans through the food chain the way classical BSE did remains an open question. Lab experiments have shown that atypical prion strains can infect humanized mice, which is enough to keep researchers paying attention, but no human case of vCJD has been linked to atypical BSE. One leading hypothesis suggests that a case of atypical BSE in a single cow may have been the original spark that, through the recycling of rendered material in feed, eventually amplified into the classical BSE epidemic. If true, that would mean atypical BSE is rare enough to be almost irrelevant at an individual level but dangerous at a systemic level if feed controls are relaxed.
Can You Catch It From Someone Else?
You cannot catch vCJD from casual contact, coughing, or sharing food with an infected person. But prions can be transmitted through blood. Five patients are suspected to have developed vCJD or a vCJD infection after receiving blood or plasma-derived products from donors who later developed clinical vCJD. All five received non-leukodepleted (meaning white blood cells had not been removed) blood products in the United Kingdom between 1994 and 1999.17PubMed. Transmission of Variant Creutzfeldt-Jakob Disease Through Blood Transfusion and Plasma-Derived Products: A Narrative Review of Observed and Modeled Risks
This discovery led to major changes in blood donation policy. Many countries still defer donors who spent significant time in the UK during the BSE epidemic. Blood services introduced leukodepletion, the removal of white blood cells, as a precautionary measure, since prions are thought to associate with white cells in the blood. These transfusion-related cases are a reminder that the risk from BSE was never limited to eating beef, even though dietary exposure was the primary route.
Sporadic CJD and Why Not Every Brain Disease Is Mad Cow
Most cases of Creutzfeldt-Jakob disease in humans are not caused by eating contaminated beef at all. Sporadic CJD, which accounts for roughly 85 percent of human prion disease cases, arises without any known external trigger. It affects about one to two people per million per year, typically striking in the 60s or 70s. Because sporadic CJD and vCJD are both prion diseases affecting the brain, they can look superficially similar, but they are distinguishable under the microscope and through molecular testing. Sporadic CJD shows a different pattern of prion deposition and does not feature the florid plaques characteristic of vCJD.18JAMA Neurology. Sporadic Creutzfeldt-Jakob Disease Mimicking Variant Creutzfeldt-Jakob Disease The prion protein in sporadic CJD also shows much more molecular variability from case to case, while vCJD cases are remarkably uniform, consistent with a single strain of prion causing all of them.19PubMed. Prion protein heterogeneity in sporadic but not variant Creutzfeldt-Jakob disease: UK cases 1991-2002
If you hear about someone dying of CJD, the odds are overwhelmingly that it was the sporadic form, unrelated to beef. The distinction matters because sporadic CJD has not increased in incidence and is not preventable through food safety measures. It is part of the background rate of human prion disease that exists independent of any animal epidemic.
The Economic Wreckage That Reshaped the Beef Industry
The BSE crisis did not just kill cattle and a few hundred people. It devastated farming communities financially and psychologically. When a single case of BSE was detected in Canada in 2003, borders slammed shut. The direct and indirect economic impact on the Canadian cattle industry exceeded six billion dollars. Five years later, researchers studying affected communities found ongoing uncertainty and stress from unrecoverable financial losses, with lasting effects on the health of farming families and the sustainability of agricultural communities.20PubMed. The psychosocial and socioeconomic consequences of bovine spongiform encephalopathy (BSE): a community impact study
The UK experience was far more severe. British beef exports were banned by the European Union for a decade. Consumer confidence cratered, and the entire structure of how beef was produced, processed, and tracked was rebuilt from scratch. The traceability systems, ear-tag databases, and slaughterhouse inspection protocols that exist today in most developed countries are, in large part, a direct legacy of the BSE crisis. When you buy a steak in 2025 and it poses essentially no risk of carrying BSE prions, that safety was purchased at enormous cost to an earlier generation of farmers, regulators, and the unlucky people who developed vCJD before anyone understood what was happening.
Chronic Wasting Disease and the Next Worry
BSE may be under control, but another prion disease in a different animal is generating fresh concern. Chronic wasting disease, or CWD, infects deer, elk, and moose across North America and has been found in parts of Scandinavia and South Korea. CWD prions are present in muscle tissue, saliva, urine, and feces of infected animals, making the disease extraordinarily contagious among cervids. The question that haunts prion researchers is whether CWD could eventually jump to humans the way BSE did.
So far, no confirmed human case of CWD-derived prion disease exists. But the surveillance challenge is immense, because sporadic CJD already occurs at a low background rate, and distinguishing a CWD-derived human case from sporadic CJD would require specific molecular testing that is not routinely performed. Public health agencies recommend that hunters in CWD-endemic areas have their deer tested before eating the meat and avoid consuming brain, spinal cord, or lymph nodes. The advice mirrors the BSE lesson: keep the highest-risk tissues out of the food supply, because cooking will not save you if prions are present.