Prions Prions have been a mistery for scientists from the day they where discovered. Prions act like viruses but they are not. Their structure and chemistry are unknown. They are believed to be proteins but that is yet to be completely proved. Prion stands for “proteinaceous infectious particles”. Prions are known to cause many diseases involved with nervous systems like the brain. They are the ones that cause the well known “ mad cow ” disesase in Britain and “scrapie” for animals. For humans they are known to cause a rare disease in Papua New Guinea called Kuru ( or “laughing death”) which striked only the