Ethics of medical testing

Would you want to know if you had an incurable, non-transmissible disease? Is the answer different if it's transmissible under certain circumstances? Should testing be cumpulsory, as a public health issue, in that case?

We deal with this sort of question with our blood supply all the time. When you donate blood, it's tested for blood-borne agents such as HIV and hepatitis. You're contacted if any of the tests come up positive, because they don't want you to keep trying to donate blood after that. But what you do about it, other than stopping the donations, isn't their concern, and they don't pursue it.

New Scientist reports on a current problem in the UK, where they have three confirmed cases of variant Creutzfeldt-Jakob disease resulting from blood transfusions. CJD is the human form of Bovine Spongiform Encephalopathy, commonly known as "mad cow disease".

A total of 66 people in UK are known to have received transfusions from blood donors who later went on to develop vCJD. Of those, 34 later died from other causes. The remaining 24 people have been informed that they may be at high risk of developing vCJD, but are not reported to have been tested.

Would those 24 want to know? There's no way to test donors or transfusion recipients during the disease's incubation period, which can be very long — indeed, an infected patient might never develop clinical disease (as with the 34 in the above quote). And there's nothing that can be done about it anyway, if one is infected.

But here's the issue:

In each of the three cases, the victims received blood from someone who went on to develop vCJD between 18 and 40 months after donating blood, which shows that apparently healthy blood donors can pose a threat of infection, at least in the late stages of incubation. Many carriers, unaware of their infection, may have transmitted the mutant prion in donated blood, experts say.

The US deals with this issue by not accepting donations from anyone who spent a significant amount of time in the UK during certain periods. That works for us, because it eliminates a relatively small portion of the donor pool, but it wouldn't work in the UK. They eliminate transfusion recipients, hoping to contain the problem.

So these are the ethical questions:

1. When a blood test becomes available, should donated blood be tested for CJD, and if the test is positive, should the donor be told? Telling the donor discourages the donor from donating again... but lets him know that he's infected with something that might or might not give him an incurable fatal disease. That's a heavy psychological burden.
2. When a donor develops CJD, should recipients of his blood be told? We have the same issue here — there's nothing they can do about it, and they might or might not become ill.
3. Ultimately, what's the best way to maintain a safe blood supply, free of CJD-contaminated blood? Do all individual concerns give way to this one?