Skip to main content
King County logo

Prions are infectious proteins that cause illness when they fold abnormally in the brain. These illnesses are sometimes called transmissible spongiform encephalopathies (TSE). The most common human prion disease is Creutzfeldt-Jakob Disease (CJD), a rare, rapidly progressive neurodegenerative disorder. CJD is always fatal, typically causing death within a year of onset. Classic CJD has been recognized since the early 1920s. Most CJD cases are sporadic (85%), and some are familial (15%). The diagnosis is confirmed by laboratory tests on brain tissue obtained by biopsy or autopsy. In recent years, the United States has reported fewer than 300 cases of CJD a year.

In 1996, a new type of CJD called "variant" CJD (or vCJD) was recognized in the United Kingdom. This type is associated with Bovine Spongiform Encephalopathy (BSE), a neurodegenerative disorder in cattle also called "mad cow disease."

Resources for the general public

Resources for health care professionals