PARIS, Aug 3 (AFP) - Deaths in Britain from a brain disorder blamed on mad-cow disease have been rising by a third each year since the phenomenon was detected, although the overall toll remains low, British scientists reported Friday.
Variant Creutzfeldt-Jakob disease (vCJD) has sparked worry among some doctors, who fear it is a disease that, like AIDS, has leapt the species barrier and could ravage the population.
In a letter to the British medical weekly The Lancet, the researchers said incidence of vCJD had been increasing by an average of 23 percent each year since 1994, and deaths from the disease had risen by 33 percent each year since 1995.
"The absolute number of cases in the UK is still low, but such an increase should be a matter of concern," they said.
As of June 30, 75 cases of vCJD had been identified by Britain's National CJD Surveillance Unit, 69 of whom had died.
Fifty-nine cases had been confirmed by post-mortem examinations of brain tissue. The other 16 cases, six of whom were still alive, are classified as probable vCJD.
However, these figures vary greatly quarter by quarter and year on year, giving a misleading picture as to whether vCJD may be spreading, slowing or has stopped.
This is because it can take years for the disease to incubate, for its symptoms to become apparent in a patient, be diagnosed by a doctor and then reported to the special monitoring unit.
The researchers, led by Rob Will from CJD Surveillance Unit, sought to provide a more even picture by establishing the onset of the disease in each case.
They did this by asking relatives when the symptoms became apparent and comparing this with the date of death.
They then grouped data about onsets and deaths into yearly and quarterly categories, to see if the disease was spreading over time.
The result suggests a steady but statistical rise in incidence and deaths that is not reflected in the raw figures.
"Given that further cases with onsets in 1999 and 2000 will probably be identified in future months, the number of onsets clearly increases each year. Already, in the first six months of this year, 14 people have died compared with 18 deaths for the whole of 1998," they said.
"(...) We believe that our findings reflect a real increase in the incidence of vCJD in the UK. Such an increase is clearly a matter of concern, although we emphasise that the absolute number of cases is low."
Like mad-cow disease -- bovine spongiform encelapathy -- vCJD is caused by a rogue protein that creates microscopic holes in the brain, turning it spongy.
The symptoms are occasional forgetfulness and eccentric
behaviour, which develop into shaking and jerky movements,
culminating in dementia and death.
There is currently no cure or vaccine, although progress has been made, among laboratory mice, towards slowing the spread of the disease and also towards diagnosing the ailment an earlier stage.
Britain is by far the nation that is the most exposed to the risk of vCJD.
It bore the brunt of the mad-cow epidemic, which has been blamed on farmers' practices of using ground-up sheep carcasses, carrying the disease, to beef herds.
Experts are divided, however, as to whether vCJD will be a long-running epidemic that will resound for decades, or a brief scare that will claim only a relatively tiny number of lives.