You wrote; “Prusiner won the Nobel Prize in Physiology or Medicine in 1997 for his discovery of prions, a class of proteins that causes CJD in humans and "mad cow" disease (BSE) in cattle..”. There is his team conclusion about transgenic mice prion  research (Scott et al, 1999); „Our findings provide the most compelling evidence to date that prions from cattle with BSE have infected humans and caused fatal neurodegeneration“. However, BSE can be a naturally occurring disease, so not an infectious disease. WHY? Because, about the BSE disease; this was never justified scientifically! It was pure, math-model-driven science fiction. But it was pushed very vigorously by the British science establishment, which has never confessed to its errors... See more about the; BSE/ vCJD mathematical- models, see recent large three comments  in Telegraph.co.uk
(www.telegraph.co.uk/.../...ic-health-threat.html).