Corruption as in "Going from saint to depraved mutant-humping deviant" - I agree, doesn't seem thematically appropriate.There will be human AI, we've just not seen much of other human NPCs yet.
I don't think corruption would work personally.
Corruption as in "Susceptibility to virus/es, contagions, etc that make one weaker and/or less effective at resisting [certain types of] enemies" - I think that could totally work. Throw in decontamination stations here n there to uhh... "wash off".
A miasma too perhaps? The longer MC is exposed to it the harder it'll be to fend creatures off perhaps, an extra layer of difficulty in that you could be 360 no-scoping all the enemies but if that pseudo Geiger counter starts peaking and for extended period of time then normally easily disposable enemies may become quite the head (or ass) ache.
/spitball