I've got this fascination with prion diseases, particularly Kuru. It's a progressive disease of the central nervous system marked by increasing lack of coordination and advancing to paralysis and death within a year of the appearance of symptoms (one of which is uncontrollable laughter, as if the person is being tickled well beyond the point that it's funny); thought to have been transmitted by cannibalistic consumption of diseased brain tissue (during ritual mortuary cannibalism) since the disease virtually disappeared when cannibalism was abandoned. Kuru is also apparently a fractional unit of money used in places like Egypt, Sudan, Lebanon, and Syria. Money is a brain disease. I can't argue with that one.