I know this is an odd, niche kink, but I've been into STDs lately. I don't care if they're real or fake, just the spect of characters getting STDs, knowingly or unknowingly, really turns me on.
Defending Lydia Collier is the only game i know of that has this. If you fuck Tanya in the nightclub's toilets, you'll get an STD and i think it's possible to pass it on to Stephanie if you're on her path.