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Last Updated:  Friday, 28 February, 2003, 10:54 GMT
Q&A: Has vCJD peaked?
Figures from the UK's National CJD Surveillance Unit suggest the worst of human BSE infection may be over.

This week, scientists predicted a total of 7,000 people will end up being infected with the disease - far fewer than the half a million originally predicted.

BBC News Online examines claims the disease may have peaked.

What is CJD?

CJD, or Creutzfeldt-Jakob Disease, is an infectious and deadly brain disease for which is there is no cure or treatment.

It causes personality change, loss of body function, and eventually death. It is thought to be caused by rogue proteins called prions.

It is a member of the same class of diseases as Bovine Spongiform Encephalopathy (BSE), commonly known as Mad Cow Disease.

Are there different forms of the disease?

There are two forms of CJD, classical and a new form, variant (vCJD).

Three types of classical CJD are recognized: sporadic, familial and iatrogenic.

Sporadic CJD, which comprises 85-90% of all classical CJD cases, occurs spontaneously in the general population with no known cause or triggering event.

vCJD is a similar neuro-degenerative disease, but generally occurs in younger people. Scientists believe vCJD is caused by eating meat infected with BSE.

How widespread is the disease?

There are about 35 to 70 cases of CJD each year in the UK. Most are of the sporadic form.

The number of cases of vCJD has ranged from seven in the year it emerged in 1995 to 27 in 2000. Last year, 16 people were diagnosed with this form of the disease.

In total, 122 people in the UK have died from vCJD, while eight are living with the disease.

Is vCJD in decline?

Figures from the National CJD Surveillance Unit suggest vCJD may have peaked.

A total of 17 people died from vCJD last year. This compares to 20 in 2001 and 28 in 2000, when the disease reached its high point. So far this year, there has been one recorded death.

Scientists at the unit say the figures are encouraging but warn that it is too early to say whether the disease is in permanent decline.

Writing in the medical journal, they warn that too little is still known about vCJD to be able to declare once and for all that it is in decline.

For instance, there could be more than one strain of the disease - one that incubates for much longer and will only emerge many years from now.

What do other scientists say?

Initially, scientists predicted that as many as half a million people could die from vCJD.

This figure was based on estimates that the incubation period for the disease could be as long as 16 years and that thousands of people could have eaten infected meat before new safety measures were introduced.

However, there is a growing consensus that the final death toll may not be nearly as high.

In August 2000, scientists from the Wellcome Trust suggested that 136,000 people could die. This figure was based on their theory that it was now more difficult to catch vCJD.

They suggested that people had to be genetically susceptible to the disease and estimated that only 40% of Britons had these genes.

This week, scientists at Imperial College London downgraded that figure further to 7,000 cases.

They said that figures for the past seven years had shown that a "dramatic increase" was unlikely.

They also suggested that young people between the ages of 10 and 20 are most at risk of contracting the disease.

They added that safety measures introduced in 1996 to stop infected meat passing into the food chain meant fewer young people have been exposed to the disease.

What will the final death toll be?

Nobody knows what the total number of deaths from vCJD will be.

The single biggest problem for scientists is that they still don't know how long it takes for a person to die once they have become infected with the disease.

The current thinking is that death occurs about one year after symptoms first appear and a diagnosis is made. However, scientists do not know when many of these people first became infected.

In addition, all those who have died have come from one single genetic sub-group. If the disease starts to affect other genetic sub-groups than the predicted death toll will rise.

Professor James Ironside, from the CJD Surveillance Unit, told the BBC: "There is evidence from other studies particularly experimental studies in mice and studies in other human diseases to indicate there are differences in genetic susceptibility that do not allow us to say with certainty that the problem is over."

All of this means, official figures from the National CJD Surveillance Unit are at the moment the best way of predicting whether the disease has peaked.

CJD cases 'in decline'
28 Feb 03 |  Health
CJD cases 'will increase'
10 Jul 02 |  Health
CJD deaths 'may have peaked'
23 Nov 01 |  Health

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