INFECTIOUS PRION. “If you ingest a prion, it may not be “flushed away” the next morning. It’s capable of crossing some species barriers. It’s resistant to food-preparation treatments such as high heat and ultraviolet irradiation. It’s stubbornly insoluble. And it knows how to find its way from your digestive system into your nervous system.”
http://www.strangehorizons.com/2004/20040216/killer.shtml