VCJD is a degenerative brain disease in humans which is thought to be caused by an abnormal prion protein in the brain. Its most likely origin is exposure to the BSE prion via eating infected BSE cattle.

So far there have been about 80 definite and probable cases of vCJD. Opinions are divided over the likely size of a human epidemic. Some scientists believe the disease could have reached its peak already. While others point to the disease's long incubation period and suggest thousands may be affected in the future.