This is actually not good stats. In the general population, the current situation with prions is that they are extremely rare. But that's for the general population. If you are around brain eaters then your risk for exposure is exponentially higher. For example, the odds that a person from the general population is exposed to HIV is relatively low. But if you instead only focus on people that live in smack houses in an abandoned part of detroit, then those people have much different odds.

The problem with prions is literally fucking everything though. There is a reason they will wipe out thousands of cows if they find out even one has prion disease. First is time. They usually do not show symptoms for a long long time. Next, is prions are damned near impossible to get rid of. So you're hanging out with brain eaters, but you aren't eating brains? But did you use their forks? Because the dishwasher isn't getting rid of that prion. Goddamn medical autoclaves do not get rid of them. I know someone that was participating in a neurosurgery, and after a couple days after the surgery, they found out the patient had a prion disease (probably Creutzfeldt–Jakob but I don't recall for sure). Well that caused havoc because of possible exposure and the lag time between the surgery and finding out. They destroyed a lot of things, had intense decontamination for others, had to inform some people in the hospital about possible exposure. Even with the low risk, just imagine being one of those people. For the next 20 years, the thought is probably just lingering in the corner of their brain that a dumbass protein that couldn't follow directions and decided to make its own rules is also lingering around a corner of their brain.

But yeah, cannibalism in general tends to lead to increased rates of disease and new diseases. Which is logical. Most diseases aren't interspecies, but if you are eating the same species then you can catch anything that has lingered. Parasites, bacteria if you like your human flesh medium rare, viruses, and prions. So I highly suggest against hanging out with cannibals.