This does not take us further forward. We've got a little piece in a very large jigsaw puzzle

Professor Liam Donaldson, Chief Medical Officer

Medical researchers in Plymouth and Edinburgh have been looking at samples of human tissue for signs of the disease which many scientists have linked to BSE in cattle.

So far there have been 53 confirmed deaths from new variant CJD, and a further two suspected cases, but some experts believe a CJD epidemic could claims the lives of thousands of people.

Scientists have analysed 3,000 samples of tonsil and appendix tissue - of some 18,000 stored after operations - in the hope that they can give early warnings of any possible epidemic.

In humans, CJD manifests itself with similar symptoms to more common illnesses like Alzheimer's Disease, such as fatigue, depression and memory problems.

The sufferer then develops shaking, and jerky movements, and eventually moves towards dementia and death.

Rough guide

Because of the small sample size and uncertainty about the how the disease develops, the results provide only a rough guide to the potential problem.

Even though no evidence of infection was found, there could still be a substantial number of affected people who could develop the disease years later.

Professor Donaldson said the results did not provide enough information to update predictions of how many people may eventually contract the disease.

"This does not takes us further forward. We have to rely on the very wide estimates that scientists have already made. It will be very many years before we can tie it down with any certainty."

He added: "This is the best we can do at the present time. There are a number of Holy Grails on this but one of them would be to have a valid diagnostic test, both on the animal and the human health sides."

"We've got a little piece in a very large jigsaw puzzle."

Professor John Collinge, a member of the Spongiform Encephalopathy Advisory Committee and head of the neurogenetic department at the Imperial College of Science, Technology and Medicine in London said the results did not provide any reassurance.

He added: "Unfortunately, these negative results do not really tell us anything at all. There are so many uncertainties."

He said it was still possible that hundreds of thousands of people are incubating the disease.

We have to remember that this was a small study of only 3,000 samples and we will want to wait and see the outcome of the rest of the study

CJD Support Network

The Government is committed to spending �26 million over the next year into research into CJD and BSE.

The spongiform disease is thought to have been transmitted to humans through infected beef.

Spongiform diseases are caused by the abnormal folding of nerve-tissue proteins, called prions, which lead to the build up of insoluble deposits building up within brain cells, which then no longer function properly and die.

Most CJD victims live with the disease for 14 months, but some survive for more than three years.

Centralised system

Frances Hall, of the Human BSE Foundation who lost her son Peter to the disease, said: "We need a centralised care package and centralised funding to make it uniform throughout the country.

"Some authorities are exemplary, you can't fault them, but in other areas it's still not good enough.

"It's no good being offered a wheelchair two weeks after they've died," she said.