AS many as 10 million Britons could be infected with a new strain of Creutzfeldt Jakob Disease (CJD) by 2010, it was claimed yesterday.
The claim was made by Dr Stephen Dealler, a British doctor investigating the link between BSE and humans.
The chairman of the committee of scientists advising the British government, Prof John Pattison, said yesterday that many more cases could emerge.
But Dr Gerard Sheehan, consultant in infectious disease at the Mater and Beaumont hospitals in Dublin, said he believes "that the whole thing is overblown".
"You have to put it in context", he told The Irish Times. "In Ireland we have up to three CJD deaths a year compared to the number of people who die in traffic accidents. Dr Dealler is generating the most alarmist situation possible.
"To my knowledge there is no evidence to support this. In terms of being concerned about the transmission of infection through the food chain, I would rank this way down the list," said Dr Sheehan.
CJD is one of a group of disorders which affect animals and humans. It is incurable and always fatal. It afflicts human beings in the same way that Bovine Spongiform Encephalopathy (BSE) damages cattle, and scrapie affects sheep.
It presents itself, according to Irish neurologist Dr Michael Hutchinson, as a progressive dementia. It is also characterised by myoclonus which are muscle jerks. CJD leaves the brain riddled with holes, as if it was a bath sponge, six Patients usually die within months of the onset of symptoms.
Scientists are still struggling to understand the disease and how it is cause The most prevalent theory is that a virus like protein called a prion, which converts normal protein molecules into dangerous ones by making them change shape, is responsible.
In Ireland up to four cases a year affect people in their 50s or 60s.
Dr Hutchinson says that CJD is "infectious but not contagious". The disease can be passed on when a surgeon carries out a brain biopsy on someone with CJD and also through corneal transplants.
Other cases were recorded in people who had received human pituitary gland growth hormone replacement therapy. This is no longer a risk, since the hormone is produced synthetically.
A ritual which involved eating part of the brain of dead people resulted in a form of CJD being recorded in an area of Papua New Guinea. The incidence of the type of the disease known as kuru decreased dramatically since 1959 when the practice was discontinued.
BSE, or "mad cow disease", was first officially identified in 1986. This was three years before the British government banned from human consumption specified offals where BSE is known to concentrate - including the brain, spinal cord, spleen, tonsils and intestines.
What startled scientists at the CJD surveillance unit in Edinburgh was that the form which the disease took in the latest victims was completely new.
They were much younger than in previous cases, with an average age of 27.5 years. People with CJD are usually over 63.
They also had unusual brain wave patterns and post mortems revealed much larger aggregates of prions in their brains than had been seen in previous cases.
The way the disease affected the brain was, however, quite different to that found in cattle with BSE. But significantly, the scientists could find no evidence of genetic causal factors.
Left with no other feasible explanation, the scientists were driven to the conclusion that the most likely cause was exposure to BSE.