In the spring of 2001, a hoax anthrax letter arrived at a Canadian government office in Ottawa. Canadian researchers conducted a series of tests, and found that if anthrax spores were made into a fine powder, then a single envelope of them could contaminate numerous postal sorting machines and entire offices. While a few people in the US government learned of the studies at the time, the Centers for Disease Control did not hear about them until November, when the anthrax attack was over.Stephen V Cole