Having been to uni and shared with people who hardly ever wash their hands (yet amazingly hardly get ill, how does that work?), everything will work out fine. Just keep up with your hand hygiene if you find out somebody is ill then use logic, it's probably because they've been drinking and besides, you'll probably have your own room which you can retreat too and keep a safe haven.

I remember one time though there was a terrible flu season and everyone was going down with it. I managed to avoid it by just keeping up good hygiene. One person I was living with brought it into the house so I just avoided them for a while and stayed in my room as much as possible until I could be sure the worst was over (eg: other people were being around them, going about their business with far less hygiene than I was and not catching it).