Early results from a British scheme studying the spread of new variant Creutzfeldt-Jakob Disease (CJD), the human form of BSE, have produced no evidence of the disease in a batch of routine cell samples. But scientists warned yesterday there was still enormous uncertainty surrounding the incubation and spread of the disease.
Government-funded scientists issued the results of the first round of CJD tests, after examining 3,170 tonsil and appendix tissue samples taken since the 1980s during routine operations.
The scientists were looking for evidence of a protein called prion in the samples which is linked to the presence of CJD in the body, but none of the results came back positive. If even two or three samples had been positive, the scientists said, this would have indicated that thousands of people could be incubating the disease.
Scientists have stressed that the results are only the first in a series of studies of the disease. A clearer indication of the size of the CJD problem will be known in about two years when all 18,000 samples have been analysed.
The chief medical officer, Prof Liam Donaldson, said the first results were encouraging, but warned against jumping to hasty conclusions. "The fact that no positives have been found is welcome news, but these early results should not be taken as an indication of an all clear," he said.
"This doesn't take us any further forward. We have to still rely on the very, very wide estimates that scientists have already made. This is a complex and mysterious disease, and the results of today's study throw a little bit more light on it, but it's very much an evolving conundrum."
It was also not possible to know at what moment during the incubation of the disease the samples might turn positive, and Prof Donaldson said scientists were not able to predict whether someone with a positive sample would go on to develop fullblown CJD.
Dr Graham Medley, an expert on CJD from Warwick University, echoed the concerns of Prof Donaldson. So little was known about CJD it was difficult to know what the scale of the threat really was, he said. "If the incubation period is 10 years, then we are in the middle of the epidemic," he said. "If the incubation time is 30 years, then we are only at the beginning. We have never before seen this disease in humans and we simply do not know at the moment."
Another expert, Prof Hugh Pennington, said he greeted the results of the study with a sense of relief. "If anything positive had come through it would have been bad news," he said.
Prof Pennington, who specialises in bacteriology at Aberdeen University, said scientists would have to wait for the results of all 18,000 samples to assess the impact of the study. "If they come up zero again, that would maybe tell us that perhaps we should not expect many more cases than we have had so far," he said.
The first confirmed case of CJD in Britain was in 1996 after the death of Stephen Churchill (19). Since then another 52 people have died from the disease and, while some scientists predict it will affect thousands of people, others suggest only about 100 people will contract CJD.