“The incubation period for classical CJD may be as long as 38.5 years. Accumulating evidence suggests that the asymptomatic incubation periods of vCJD may be very long as well (sometimes exceeding 12 years from the time of exposure to the BSE agent), ….” FDA FAQ.
I used to be a regular blood donor until the new rules on Mad Cow Disease (CJD) cut me out. I lived in the U.K. for a year in 1990/91 (amazing time to be there too) and even though I was and still am not a meat-eater (not a veggie though – I do eat fish) I suppose One Never Knows, as they say, or at least as the FDA and other blood regulators say. But I do keep up with the regulations and cross my fingers that I will either pass the cut-off date or a test for CJD will show up and I will be able to donate blood again. I was one of those odd people who always felt BETTER after donating blood. (Maybe I just have too much of it :-). But when I saw the above FAQ from the FDA recently, I threw up my hands – 38.5 years! Good grief, as Charlie Brown would surely say.