12674人の虫垂と扁桃腺を調べたところ3人がvCJDの兆候を示し、全英国民では最終的に3800人が罹患すると予測されていた。しかし3人のうち1人だけが実際に発病していて、後の2人は科学者が検体から予測したようなvCJDの発症者ではなかった。また、昨年までの全発症者の遺伝子が一つのサブグループに属しており（国民の40％）、これらのことからBSE汚染肉を食べてvCJDに感染しても発症しない人もいると考えられる。予測では数千人がvCJDキャリアであるが発症するのは70人という結果になった。しかし別の遺伝子群に属する者が輸血により感染したことが明らかになった。仮に新感染者の遺伝子がこれまでの患者同様に感染しやすくて潜伏期間は長いというものならば、最悪で将来600人が死亡すると言う予測になっている。しかし、これまでの予測より患者数が少ないのは潜伏期間が寿命より長いという人が多いからではないかと言うことも一因と考えられ、そのような人が自身がキャリアであることを知らずに輸血を行えばそれにより感染者数がどれくらい増えかは予測がつかないと言う。科学者達はより正確な予測の為に研究を行うとしているが、Human BSE財団のFrances Hallは「数の予測をしても患者や病気を心配する人の為にはならない」と病気の早期の判定方法を開発することに重きを置いて欲しい」としている。

http://news.bbc.co.uk/2/hi/health/4162749.stm
Last Updated: Wednesday, 12 January, 2005, 01:23 GMT
'vCJD timebomb' fears discounted

*High numbers of future deaths in the UK from the human form of mad cow disease are unlikely, researchers have said.

The Imperial College team calculate there will be around 70 future deaths.

They say, the worst case scenario could see another 600 deaths, but that this was unlikely.

The research, which appears in the Journal of the Royal Society, said thousands of people could carry vCJD, but show no symptoms.

The higher forecast is based on the possibility that people from different genetic subgroups could be affected by vCJD.

So far, only people of one genetic subgroup, which accounts for 40% of the population, have been affected.

*Tonsil samples

There have been 148 deaths from new-variant Creutzfeldt-Jakob disease (vCJD) since the condition was first seen in 1995.
Research pointed to eating meat contaminated with Bovine spongiform encephalopathy (BSE) as the cause.

Over the last decade, scientists have been working to evaluate what the full extent of the vCJD epidemic will be.

Deaths have been declining from their peak of 28 in 2000 to nine last year.

But researchers who tested 12,674 appendix and tonsil samples found three showed signs of apparent vCJD, indicating around 3,800 people could ultimately be affected.

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.

If this was the case, looking at the population who would have eaten infected meat, they used computer programmes to estimate there could be a total of around 70 deaths from vCJD.

In addition, the Imperial team considered research into the genetics of those who could be affected.

Until last year, all of those affected had been from one genetic subgroup. But it was then revealed that someone with a different genetic make-up had probably become infected with vCJD after a blood transfusion.

The researchers say that in this worst case scenario - if people with other gene variants are equally as susceptible as those in the original subgroup, but have a longer incubation period for vCJD - there could be a total of around 600 deaths from vCJD.

*Blood transfusions

Dr Azra Ghani, from Imperial College, said: "Since 2000 there has been a decline in the number of clinical cases reported.

"One reason for the discrepancy between the high estimated number of positive tests and low number of actual recorded clinical cases could be that infected individuals do not go on to develop clinical disease in their lifetime."

However, the researchers say they have been unable to calculate how many vCJD cases could result in the future from blood transfusions from people who do not know they are carriers of the disease.

Dr Ghani said: "Although our results indicate there is little chance of large numbers of vCJD infections from primary transmission, we have not taken into account possibility of additional cases infected by blood transfusion.

"This could result in more clinical cases emerging at a later date."

The CJD Surveillance Unit said predicting the extent of vCJD was very difficult, but said the more research was carried out, the more accurate predictions could be.

But Frances Hall, of the Human BSE Foundation said she would rather see researchers focus on developing a test that could pick up early signs of the test in those who were affected.

"I don't think estimates of numbers makes a lot of difference to people who have been affected, or people who are worried about it."

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