Swiss scientists have begun collecting tissue samples from people undergoing routine surgery to screen for human forms of BSE or mad cow disease.
The study, the first of its kind in continental Europe, has opened a debate about whether people found to be carrying the deadly illness should be told.
Adriano Aguzzi, a neuropathologist at the University Hospital in Zurich, told swissinfo that doctors plan to collect at least 1,500 samples over the next five years.
While Aguzzi says the disease is currently one of the most rare, the research is vital to ensure it stays that way. "After all, we might be witnessing the beginning of a major health crisis," he says.
In recent years, Switzerland has seen a surge in cases of Creutzfeldt-Jakob disease (CJD) - a fatal brain illness that may be linked to the eating of cows infected with BSE.
Patients' details kept under lock and key
Although Britain has been doing similar research since the early 1990s, the Swiss study is unique in that patient's details will be stored in escrow by an independent third-party.
Aguzzi says the tissue samples - usually tonsils or appendices - will be numbered, and linked to a database containing patients' clinical information.
Patients must also give their consent before the samples are collected.
"We are very aware of the ethical consequences," says Aguzzi. "But the link between the clinical information and the number will not be in my hands... so I will not have the possibility to trace back who has been tested positive."
Patients' details can only be released from a secure safe if scientists find a cure for BSE, or individuals wish to know whether they are carrying the illness.
"Under those circumstances it would be unethical not to identify the patients, which is the main reason we don't want an anonymous study. We want to be able to trace back patients if need be," says Aguzzi.
Surge in Swiss cases
Switzerland, unlike its close neighbours Germany and Austria, has seen a sudden surge in new cases of CJD - well above what researchers consider the standard rate of one case in a million.
Until recently, the number of cases in Switzerland - typically six or seven per year - was similar to that of its neighbours.
"[But] in the past two years however, we have witnessed a drastic increase," says Aguzzi.
Last year 19 cases were recorded, while this year the same number has been identified up to the beginning of October. The most recent case was reported on Monday.
"Obviously something is going on, and we do not quite exactly know what that is," he warns.
Five potential causes?
Aguzzi says the increase in Swiss CJD cases could be caused by one of five things - each of which is being investigated.
The first theory - which cannot be scientifically proven - is that the Swiss increase is merely a statistical anomaly.
Secondly, Aguzzi says researchers have investigated whether the increase is a result of hereditary factors - something that has been discounted.
Aguzzi says the third possibility for the increase - that more cases are being uncovered because doctors, and the public, are more aware of the illness - does not explain why Austria, and Germany (which are equally active in screening for the illness) have seen no corresponding increases in their CJD rates.
Another theory - that the illness may have been transmitted through the use of contaminated blood or surgical equipment - is one Aguzzi is taking seriously.
"This is something you have to search for. You have to interview the patients - [but] often the patients are dead or already demented - so you have to find the relatives and find out exactly what the medical history has been, sometimes for operations that happened ten or 15 years earlier.
Aguzzi says his Zurich-based team is halfway through investigating whether accidental contamination may have caused the increase in CJD. "For the time being we have not been able to find any hint [that this hypothesis] is true.
The spectre of mad cow disease
"The final hypothesis is, of course, that BSE is the cause... The evidence is thin, or non-existent," says Aguzzi. But still something that needs to be discounted - hence the tissue sample study.
In Britain, where the tonsils and appendices from some 8,318 patients have been tested since the late 1990s, only one potential case of the bovine brain disease has been found.
Among the tissue samples, researchers found a positive sample of the prion (or misshapen protein) thought to cause "variant" CJD - a version of the disease, not yet seen in Switzerland, which tends to affect younger people.
The finding, which was announced last month, has led to estimates that about 120 out of every million Britons might eventually develop vCJD.
While all the cases recorded to date in Switzerland involve what is considered "classic" CJD, doctors cannot discount the possibility - however remote - that they may have been triggered by BSE, as in the British case of vCJD.
Doctors in France and Germany are carefully monitoring the results of the Swiss study, which Aguzzi hopes to expand to hospitals around the country in coming months.
swissinfo, Jacob Greber
Creutzfeldt-Jakob disease is an incurable, fatal brain illness.
Swiss CJD cases this year (to early October) - 19.
Swiss cases in 2001 - 19.
Swiss cases in previous five years - 45 (an average of nine per year).
Normal average for countries that conduct screening - one person in every million.
University Hospital in Zurich hopes to collect samples from at least 1500 patients.
Results will only be made available to individuals if cure for CJD is found, or patients want to know.