Creutzfeldt-Jakob Disease can happen spontaneously, meaning one of your prions becomes misfolded. It can also be genetic or caught due to medical equipment that hasn’t been properly cleaned or from using human tissue from cadavers (iatrogenic). There’s even been a case of variant CJD from packed red blood cells.
Have a merry Christmas!
You should see my reply to the other guy in this thread. You’ll feel so much worse.