I'm of the opinion that prions occur more often than we know, it's just that to be a prion "disease", you need more properties than just spreading the misfolded

I'm of the opinion that prions occur more often than we know, it's just that to be a prion "disease", you need more properties than just spreading the misfolded shape. Importantly a critical property is that it needs to be damaging enough to be noticeable and neural matter has the unfortunate property that it heals slowly (if at all) so low level damage can accummulate.