About Prion Diseases

Key points

  • Prion diseases are a family of illnesses that affect people and animals.
  • These diseases are rare but always lead to death in the person or animal within months to years of symptoms beginning.
  • There is no treatment or vaccine.
Images of a cow, an elk, slide of CJD affecting the brain, and a case of beef products.


Prion diseases occur when proteins normally in the body misfold and cause illness. The misfolding leads to brain damage and other symptoms. Symptoms may take years to develop. But once they do, the disease rapidly progresses and leads to death.

Some of the reasons people may get sick with prion diseases is eating or handling meat contaminated with prions. People may also become infected if they get prions in their bodies. This may occur through organ transplant or being exposed to contaminated equipment during surgery.


Prion disease in people

Many different prion diseases affect people, but some are more common than others. The most common prion disease in people is Creutzfeldt-Jakob disease (CJD). Another prion disease, variant Creutzfeldt-Jakob disease (vCJD), has a similar name but is a different, much rarer, disease.

Other prion diseases include kuru, variably protease-sensitive prionopathy, sporadic fatal insomnia, and inherited forms caused by genetic mutations.


CJD is a prion disease that causes a person's brain to break down or stop working normally. Once symptoms start, the disease progresses quickly. It is always fatal, usually within a year.

CJD is sometimes called "classic CJD" to avoid confusion with variant CJD. Most cases of classic CJD are in older people. They appear sporadically. This means there is no known reason that the cases begin.

A smaller number of cases occur in people who inherited genetic changes that make them prone to CJD. Occasionally, there have also been illnesses in people who were exposed to surgical equipment or other products contaminated with prions.


vCJD is tied to eating beef from a cow that had a prion disease called Bovine Spongiform Encephalopathy (BSE). It was discovered in 1996 in the United Kingdom.

The disease affected much younger people than CJD. vCJD often infected people their 20s or younger. It caused mental symptoms and behaviors, as well as pain when touching things (dyesthesiasis), that CJD does not.

There have only been four vCJD cases reported in the United States. All occurred in people who were likely exposed to BSE outside the U.S.

Myths and misconceptions

Though they have very similar names, CJD and vCJD are very different. They affect different groups of people and have different causes.

They have different symptoms and affect the body differently. [Table goes here]

How animals are affected

Prion disease in animals

There are a number of known prion diseases in animals. The two most important in the United States are bovine spongiform encephalopathy (BSE) and Chronic Wasting Disease (CWD).


BSE is a type of prion disease that affects cows. The first cases were identified in the mid-1980s, but BSE didn't gain widespread attention until a major outbreak in the United Kingdom later that decade into the 1990s. Millions of cows were infected.

By 2005, 24 countries had reported BSE among native cattle. (20 of the 24 were in Europe).

The first BSE case in North America was reported in 1993 in a cow imported into Canada from the United Kingdom. Additional BSE cases were identified in Canada beginning in 2003.

Later that year, a cow in Washington State also tested positive. The cow had come from a Canadian farm prior to being imported into the United States and was likely exposed there. This case remains the only classic BSE case identified in the United States, although cases of atypical BSE have been found.

Experts eventually concluded that the spread of infection in cattle was likely tied to feeding practices. They speculate it began when cows were fed meat and bone meal from other cows that had prion disease.


CWD is a prion disease that affects animals like deer, elk, moose, and reindeer. It has been found in the United States, Canada, Norway, Finland, and Sweden. Imported cases have also been reported in South Korea. First recognized in Colorado in the late 1960s, CWD has now been identified in 32 U.S. states.

Though there have been no cases of CWD in people, experts think it poses a theoretical risk to people. This is because CWD is related to BSE, which has caused disease in people. If CWD could spread to people, hunters and people who eat meat from CWD-infected animals would likely be most at risk.