| Think of cross-contamination as a smell. Spores of a few microns size are like the odor that comes from, say, cigarette smoke, or perfume, or any other material that sends out small particles that affect our olfactory nerves. So, if you placed a cigarette butt inside an envelope and sealed it, you would still smell it from outside the envelope, because small particles would go through the paper. If you put another envelope next to it, you would probably not smell it on the other envelope, but a blood hound, with a much keener sense of smell, probably would. Anthrax spores are at the upper end of particle sizes that stimulate our olfactory nerves, and they can be carried as well as a weak scent would be. The question is not so much could cross-contamination happen on another letter rubbing up against a contaminated one, but how far and long would that remain. Even smells die out after a while. Also, if the smell was strong enough to affect someone in a distant spot, why weren't others also affected, all along mail routes out of Trenton? Just as blood hounds can trace where someone has walked all along their route. One answer may be that the victim was 94 years old, and she may have been that rare case for which 10 spores were a lethal dose. Others along the route may have received much more, yet not been affected. I doubt that is the case, but it is theoretically possible. |
