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Last Updated: Thursday, 5 August, 2004, 22:54 GMT 23:54 UK
Q&A: vCJD numbers
CJD slide
vCJD is a fatal brain disease
Scientists have published the latest estimates on how many people may become infected with vCJD.

What is vCJD?

Variant CJD or vCJD is the human form of BSE. It first emerged in 1995 and has so far claimed 143 lives in the UK.

The disease, which affects the brain, is believed to have passed from cattle to humans through meat infected with the disease BSE.

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

Doctors are testing a number of experimental treatments. However, as yet there is no cure.

What does this latest study suggest?

The Imperial College research used computer models to look at how many vCJD cases may occur in the future.

Last year, tests on 12,674 appendix and tonsil samples found three showed signs of apparent vCJD, indicating around 3,800 people could ultimately be affected - a much higher number than was suggested by the number of deaths seen so far.

However, only one of the three positive samples actually matched those taken from people who had been diagnosed with the clinical disease.

Interpretation of the other two samples was less certain because they did not look like scientists expected them to. The Imperial College team suggest this could mean that some people could be infected with vCJD, but not develop symptoms.

Looking at the population who would have been exposed to BSE-infected meat, they suggest this could mean there will be 70 more cases of vCJD in the future.

Could the number be higher?

Possibly. So far all the people who have been confirmed as having vCJD have belonged to one genetic subgroup.

But last year, it was revealed there had been a probable transmission of vCJD via a blood transfusion to someone who was of a different subgroup.

The Imperial researchers say that, if people with different genetic make-ups - who could possibly have a longer incubation period than those who have become ill so far - are at risk, there could be around 600 more deaths.

But they say this scenario is less likely.

What are the risks of contracting vCJD now?

Tight rules have been introduced to ensure that BSE infected meat does not enter the UK food chain.

The focus now is on trying to reduce the risks of one person transmitting the disease to another person.

For instance, white blood cells have been removed from all blood used for transfusions since 1999.

This followed advice that if there was any risk of the disease being transmitted through blood, it was most likely to be found in these cells.

Blood products, such as clotting agents, are now only made using plasma from the United States.

Children born from 1996 onwards now only receive plasma that has been imported from the US.

The government banned people who had a blood transfusion after 1980 from donating blood.

And potential donors who are unsure if they have had a transfusion and those who regularly donate blood components will be also be covered by the ban.

The Department of Health is spending 200m on improving its procedures for decontaminating surgical instruments, to reduce any risk of the disease being transmitted in this way.

But the Imperial researchers say there is a possibility that people who are carriers of vCJD, but who do not know they are, could pass the disease on to others via blood donation - which would mean many more could be affected.

Second case of vCJD 'via blood'
22 Jul 04 |  Health

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