Almost half of them were found to have classical CJD, the always fatal disease that afflicts one in a million people each year. Three people from France and one from Ireland have also died. The first sign is psychiatric problems, and it can also interfere with sight, hearing and sense of smell. Then comes poor muscle co-ordination, muscle spasms and mental confusion. Most victims are dead 13 months after their first symptoms appear.
Scientists know that various forms of prions have been around for a long time.
They cause classical CJD in humans, scrapie in sheep and a disease known as chronic wasting disease in deer and elk. The prions responsible in these cases are thought to arise sporadically in one in a million people and animals a year. Until mad cow disease appeared, prions were not thought to jump from species to species. What is so unnerving about mad cow disease is its apparent ability to move from cattle to people. Though mad cow disease has not been detected in people or cattle in Canada or the United States, the related prion disorder, chronic wasting disease, is spreading among deer and elk herds.