Two new diagnostic tests -- one that screens urine and the other nasal swabs -- can detect prions associated with brain-wasting diseases. The urine test was only effective for the variant form of Creutzfeldt-Jakob disease, seen in humans exposed to tissue from cows infected with bovine spongiform encephalopathy. As many as 1 in 2,000 people in the U.K. may be carriers of the BSE-linked prion, although it's not clear how many of them will develop illness.