CJD epidemic 'unlikely'

15 people have died from vCJD disease so far this year

Scientists believe that an epidemic of the human form of mad cow disease is unlikely.

Research carried out at the University of Oxford, UK, suggests that the likelihood of millions of people dying from variant Creutzfeldt-Jakob disease (vCJD) are slim.

However, researchers have suggested that deaths could still reach as high as 136,000.

Previous studies have suggested that millions of people could be at risk and last year European Union scientists estimated that 500,000 could die from vCJD.

But the researchers, at Oxford's Wellcome Trust Centre, say the total number of deaths could be under 100, or as high as 136,000.

The final figure, they say, depends on how long the disease takes to incubate - something scientists have yet to discover.

Cases per animal

The Wellcome Trust team said the reason for the fall was because they believe it is harder for humans to catch vCJD than previously thought.

"The current data suggest that, on average, no more than two cases of vCJD could arise from the consumption of one maximally infectious bovine," they said.

We have to be cautious, there have already been 15 cases of vCJD this year

Clive Evers, CJD Support Network

A year ago, the Wellcome Trust Centre suggested that there could be 100 cases of vCJD for each infected cow.

"This suggests a substantial species barrier, given that thousands of people might eat material from a single animal."

Some 750,000 cattle infected with mad cow disease, or BSE, were slaughtered for human consumption between 1980 and 1996.

Writing in the latest issue of the scientific journal Nature, they add that only people with a genetic predisposition to the disease could be infected. About 40% of the British public are estimated to have these genes.

Figures released this week show that there have been 79 cases of vCJD in the UK to date.

Dr Azra Ghani, one of the authors of the study, said that a species barrier ruled out an epidemic.

"Because the case numbers have been going up but not as dramatically as could have been the case, we believe the agent is less infectious.

Dr Azra Ghani said humans are protected by a species barrier

"That is because of a species barrier which simply means it is difficult for the agent to pass from cow to humans."

Caution

Clive Evers, chairman of the CJD Support Network, said the findings should be treated with caution.

"We might take some encouragement from these figures. However, we have to be cautious, there have already been 15 cases of vCJD this year which is a significant increase on last year.

"It could still be the case that we are talking about thousands of people being affected in the future."

He added: "We need another five years' figures before sound statistical predictions can be made."

Health officials in Leicester are investigating a cluster of vCJD cases in the area as part of efforts to find out more about the disease.

Five people living in the same area died from the disease.

Dr Philip Monk, from Leicester Health Authority, said their inquiry is aiming to establish how people were infected.

"We are never going to be able to say that it was that cow, from that farm, but what we hope we will be able to say is that it was that pattern of food consumption that led to that risk."