THOUSANDS could die in Britain from variant Creutzfeldt-Jakob disease,
computer models predict.
Last week, the British government announced a multimillion pound compensation
package for those who have already fallen victim to vCJD. A trust may also be
set up to compensate future victims. But we still do not know how many people
will ultimately be killed by the human form of BSE.
The number of vCJD victims has been steadily increasing
(see Graph). Christl
Donnelly and her colleagues at Oxford University have used those numbers to
predict how many will succumb. They estimated various values for unknown
variables, such as when cows with BSE become infectious and how long humans
incubate the disease. Then they plugged five million combinations of these
variables into a computerised model, and checked which of the resulting
epidemics fitted the numbers and ages of victims so far.
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Of the epidemics that matched, none claimed more than 136,000 victims
(Nature, vol 406, p 583). But the calculation assumed that vCJD will strike only
certain genetic types and younger age groups. If this is wrong, as now seems
likely following the recent death of a 74-year-old vCJD victim, the predicted
total could double.
It is clear that the epidemic is starting to take off. So far 24 people have
died of vCJD in Britain this year, up from 14 in 1999. Donnelly calculates that
if the epidemic had kept growing slowly, with no more than 15 deaths per year
for another few years, the toll might not top 20,000. That now looks unlikely.