Variant CJD — variant Creutzfeldt-Jakob disease, abbreviated vCJD — is the human form of mad cow disease (BSE), first recognised in the 1980s and 1990s, striking unusually young people. It is caused by prions — misfolded proteins — transmitted through eating beef from BSE-infected cattle before feed controls were imposed. The prions accumulate in the brain over years or decades, causing progressive neurological decline that is invariably fatal, with no treatment available. The outbreak transformed food safety: the UK banned specified risk materials such as brain and spinal cord from the food chain, overhauled cattle feed rules, and tightened blood-donation safeguards. New cases have dwindled to almost none, but surveillance continues.