Leading Article: When knowledge is dangerous

THE DISCOVERY of a means to predict the emergence in patients of the human variant of CJD, or "mad cow disease", raises fearful dilemmas. The Government's intention to test anonymously more of the appendices removed in hospitals, which may contain a protein associated with the virus, is only sensible. The extent of the danger posed by new-variant CJD has to be discovered, and quickly; the cases diagnosed so far could only be the first signs of a large epidemic.

But a long-term view suggests wider questions. What happens if further investigation shows the disease to be widespread? What will be the consequences of regularly examining removed appendices for signs of the virus? How will patients react to these results? Patients have a right to know - or to refuse to know - if they have a dangerous disease. But can this knowledge be hidden from insurance companies? If not, and if the disease turns out to be a certain killer, its younger victims may be corralled into a world without life insurance or mortgages. The only alternative which presents itself, to prevent creating an incentive for lying, is to give patients the right to refuse examination.

But the danger this presents to public health rules out such an approach. CJD may be transmitted via organ or blood transplants, and it would be reckless in the extreme to ignore a chance of screening the infection out of those vital procedures. Allowing CJD carriers to walk away from a chance to monitor the long-term impact of the virus would also be irresponsible. There is no way of destroying our knowledge; the genie cannot be put back into the bottle. DNA testing and genetic science will increasingly inform us of the risks we face in life. We shall have to get used to such dilemmas and become more rigorously prepared than we have been shown to be by this discovery.