After the great successes of modern hygiene and medical microbiology,
many people thought the threat of infectious diseases had disappeared. However,
emerging and re-emerging infections with more or less pathogenic potential
disproved this opinion. The onset of the AIDS epidemic has brought the
old problem of slow virus diseases to general attention. For many years, it had
been postulated that some of those diseases, particularly of the brain, were
caused by unconventional viruses. Infections with these agents do not induce
classical inflammations – acute or chronic encephalitis due to a specific immune
reaction – but a slow and irreversible degeneration of the central nervous
system presenting as encephalopathy. Those diseases had been considered rare
events in animals and humans, only interesting medical and veterinary doctors
and scientists – scrapie in sheep and Creutzfeldt-Jakob disease (CJD) in man
were known only to specialists. The onset of the bovine spongiform encephalopathy
(BSE) epidemic in Great Britain completely changed the situation. The
fatal risk of consuming contaminated beef became a topic. And indeed, the
fears were materialized when the first cases of new variant CJD (vCJD) were
identified.