One of the questions used to screen blood donors in the U.S. is whether they lived in the U.K. in the early 1990s. If you answer "yes," you can't donate. The r

One of the questions used to screen blood donors in the U.S. is whether they lived in the U.K. in the early 1990s. If you answer "yes," you can't donate. The reason is the outbreak there of bovine spongiform encephalopathy (BSE, aka "mad cow disease") and the human variant mentioned in the article, Creutzfeldt–Jakob disease (vCJD) which may lie dormant for decades IIRC.