Researchers at Imperial College, London this week revealed the first direct evidence appearing to show that mad cows disease has been transmitted to humans.

The study, carried out by a team led by John Collinge and published in Nature, is said to "greatly strengthen" the conclusion that the new variant of Creutzfeldt-Jakob Disease identified in humans is a direct result of the BSE epidemic in British cattle. New analytical techniques developed by Dr Collinge as part of the research may lead to a rapid diagnostic test for the disease.

Sheila Gore of the Medical Research Council's biostatistics unit in Cambridge says: "This is an important paper that shows that the molecular signature for BSE in animals and in the variant CJD cases where dietary exposure is suspected, is the same. There are now far fewer doubts about the link."

The study promises to make a valuable contribution to monitoring of variant CJD and help with epidemic projections, she says.

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For Steven Dealler of Burnley Hospital Trust the big question now is how many people will contract variant CJD.

His own analysis suggests a peak in humans with variant CJD could occur around 2015. In the years leading up to this peak, numbers would rise very slowly for several years and then rapidly.

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"The absolute size of the epidemic would be difficult to predict until we are well into it and actually seeing the numbers," he said. "The only way adequately to predict the numbers likely to die of the disease is by looking in the population for the number that are incubating the disease."