I don't think I've ever read manga where people get aids...There are probably a few, though.
Also "in theory", if Chino sensei doesn't have sex with other people outside school, it should be relatively safe, I think.
It's so insane how casual people are about raping others in this manga, those fucking little shits a full blown predators, imagine having your way with someone while they're asleep and think it's perfectly fine