快猫短视频

THE horrific possibility that millions of people in Britain will fall victim
to the human form of BSE is looking increasingly remote. The latest figures
suggest that the final death toll is likely to be on the scale of thousands
rather than millions.

Researchers at the Wellcome Trust Centre for the Epidemiology of Infectious
Disease in Oxford have worked with statistics on how many infected cows were
slaughtered, how much infected material entered the food chain and the course of
the cattle epidemic. From this, they have produced a model describing the likely
course of Britain鈥檚 epidemic of new variant Creutzfeldt-Jakob disease (vCJD),
the disease linked to the consumption of BSE-infected meat.

With this model, they can use figures on the number of cases in 1999 and 2000
to predict the maximum size of the epidemic. 鈥�1999 may be a bit of a turning
point,鈥� says Christl Donnelly, a statistician on the team.

If 15 people or fewer died from vCJD in 1999, the model predicts that any
epidemic will reach a maximum of half a million cases in total. If there is no
increase and a similar number die in 2000, then it predicts that any epidemic
will peak at a total of 14 000 cases or fewer. So far, nine deaths from vCJD
have been confirmed for 1999, according to the national CJD Surveillance Unit in
Edinburgh. It is still too early to put a final figure on the year鈥檚 toll, but
the current figure is less than that reported for 1998 at this stage last year.
In January 1999, 12 deaths had been confirmed for 1998, a figure that eventually
rose to 17. 鈥淚t鈥檚 good news that we haven鈥檛 seen so many cases so far,鈥� says
Donnelly.

The model assumes that only a certain proportion of the population is
susceptible to vCJD. All the known vCJD victims had two copies of a particular
variant of the gene for a protein called PrP. This trait is shared by about 40
per cent of the British population. However, it could be that other people are
also susceptible, but will take longer to display symptoms.