IT will take up to four years before scientists can say with any certainty how large the epidemic of Creutzfeldt Jacob Disease will be.
A new study published yesterday showed that Britain could conceivably face just a handful of cases of the disease, caused by eating beef contaminated by BSE, each year for the foreseeable future. Alternatively, deaths could run into many thousands.
The study used mathematical, models to predict the likely spread of nvCJD (new variant CJD) on the basis of cases being detected now. It concludes that in a "worst case scenario" there might be up to 80,000 human infections in the UK arising from BSE tainted beef.
However, researchers stressed this was an unlikely worst case and that so far there were encouraging signs that there would be only a small number of cases.
"We don't know and we will continue not to know for several years at least, and that, we appreciate, is a very unsatisfactory conclusion to come to," said Prof Peter Smith, a member of the British government's spongiform encephalopathy advisory committee.
There has been no reported case of nvCJD in Ireland. Last night Dr Gerard Sheehan, consultant in infectious diseases in Beaumont and the Mater Hospitals said matheinatical predictions of future - epidemics were "based on theory and not on fact".
"You are left, as in this case, with uncertainty as to whether there is a real problem or not," Dr Sheehan told The Irish Times.
Stressing that he had not seen the study, which has just been published in the science journal Nature, Dr Sheehan said that CJD was a very rare disease and the new variant even rarer.
"There have been a lot of mistakes made in predictions about epidemics. You only have to look at what was being said about AIDS internationally in 1985. That has turned out to be wrong. We have one or two cases of CJD here a bear. It is exceedingly rare. I am sceptical, but the point is that no body knows if it will be a big problem."
Prof Smith and colleagues report in Nature this morning that if the number of cases of the new CJD, linked last March to BSE in Britain, remained roughly constant at less than 20 a year over the next few years, then the final size of the epidemic might well be counted in the hundreds.
Uncertainty arises because the incubation period of the disease is," not known. There have been only 14 confirmed cases of CJD to date in the UK.