There seems to be some confusion as to what a prion is. Since it's such an important part of the story, I feel like an introduction is in order.

Prion is short for "protein infection" and is not something I made up.

From the wikipedia:

Prions are infectious agents composed entirely of a protein material that can fold in multiple, structurally abstract ways, at least one of which is transmissible to other prion proteins, leading to disease in a manner that is epidemiologically comparable to the spread of viral infection. Prions composed of the prion protein (PrP) are believed to be the cause of transmissible spongiform encephalopathies (TSEs) among other diseases.

Prions were initially identified as the causative agent in animal TSEs derived from scrapie in sheep and later bovine spongiform encephalopathy (BSE)—known popularly as "mad cow disease". Human prion diseases include Creutzfeldt–Jakob disease (CJD) and its variant (vCJD), Gerstmann–Sträussler–Scheinker syndrome, fatal familial insomnia, and kuru. All known prion diseases in mammals affect the structure of the brain or other neural tissue. No effective medical treatment is known. The illness is progressive and always fatal.