My roommate only washes up if he poops, never after peeing. Now every time I’m in any of the common areas I have to wash my hands after touching anything I haven’t wiped down. Thus, I wash my hands twice every time I use the bathroom; once as normal and again in the kitchen because I touched the taps, light switch and door handle in the bathroom which likely have groin sweat on them… /rant
Next time you get sick, for any reason, just blow up on him. “I got sick because you can’t wash your goddamn dick sweat and piss after you pee!”. Make it dramatic. He’ll fear you’ll blow up every time you get sick. Or bring friends over and let them go “ewww, did you just leave the toilet without washing your hands?”. Bonus points probably if it’s the sex he’s attracted to that tell him.
On a serious note: I always wash my hands. WTF?