British Columbia

CWD doesn't appear to have been created in a specific experiment, but has emerged multiple times wherever elk were kept in close captivity. It's possible that it occurs when enough randomly misfolded PrP can build up to levels where it can be transmitted between animals, much like all other prion diseases. Source: I live near "ground zero" in Saskatchewan where it escaped from elk farms and no longer hunt deer or eat deer meat. Have done a lot of research on the topic as the environmental impact is devastating.

"When it crosses to humans" is not a sure thing. Prions are not like other infectious diseases and cannot evolve in the same way. While it's possible that humans could be infected by PrP^CWD^ this does not mean that human PrP will be folded into more PrP^CWD^ but it's more likely to fold into an intermediate dead-end form. In fact this is the reason that hunters are not dying everywhere from CWD, and why the death toll from BSE was so remarkably low despite broad exposure. Prions are thankfully not very compatible across species.

CWD cannot "breed" in humans to create a human form because it's not alive. It's not even questionably alive like viruses are - it's just a protein in an unfortunate shape that catalyzes more of itself to change shape. It's a very odd evolutionary defect that PrP is normally folded into a state that is not its lowest energy state, and we're fortunate that PrP appears to be the only protein that is "broken" like this. The human form of the disease is called "kuru" and it only occurred in rare cannibal societies.

Even real infectious zoonotic diseases often have a dead-end form like this when crossing species. As a sheep farmer I'm very familiar with the viral disease we call "orf" which I have caught from sheep several times on my hands. It creates a horrifying looking sore, but when the sheep virus infects human cells, the incompatible cellular machinery cannot create viable infectious particles. As a result, it's only contagious from sheep to humans - not from humans to humans - and cannot spread from the initial infection site, either.

So worry about CWD destroying the ecosystems of North America (and Europe as some absolute morons imported deer from NA) but not about catching it, especially from eating things that are not deer, moose or elk.