Prions and prion diseases.

Currently known transmissive spongiform encephalopathies in humans and animals are presented. Caused by prions, they are known as "prion disease". The results of extensive investigations of prions are described, as well as the theories about their nature. Relating to the occurrence of the epizootic of bovine spongiform encephalopathy in England, its causes and consequences as well as the research on possible relationship between this encephalopathy and the Creutzfeldt-Jakob's disease are discussed.