Our knowledge of CJD goes back to earlier studies of kuru, the so called headhunter disease seen in Papua New Guinea, where people became infected after eating the brains of their foes and preparing their dead relatives for burial. Kuru and CJD should be thought of as two different spongiform encephalopathies. Kuru studies were instructive since they showed for the first time that a slowly progressive neurological disease of humans can be infectious, that is transmitted from one person to another. For this discovery Carleton Gajdusek was awarded the Nobel Prize. You've mentioned prions.
Prions are the most bizarre infectious agents ever imagined.
It was Stanley Prusiner of the University of California, San Francisco, who first discovered the nature of prions and suggested they are the causative agents of the spongiform encephalopathies. For this he won the prestigious Lasker Prize two years ago. They consist of a single molecule containing about 250 amino acids, termed the PrP protein. They are abnormal variants of proteins that occur normally in cells, such as human brain cells. Amazingly, abnormal PrP proteins, when they enter the body, are able to convert their normal counterparts into more of the abnormal forms.