> prion escape and becoming common in populations would be a large disaster.
IIRC, all known prion diseases are only transmissible by ingestion of infectious particles - meaning, eating from infected parts of a carcass, urine/feces and blood.
There does not seem to have been any ingestion in these two cases. Still, they do not involve transmission through air or through casual contact, but see the last couple of sentences here with regard to the former: https://news.ycombinator.com/item?id=27984942
IIRC, all known prion diseases are only transmissible by ingestion of infectious particles - meaning, eating from infected parts of a carcass, urine/feces and blood.