I had an RN tell me that one of the best things you can do in regards to certain types of "bugs" around is to wash your hands. She said what used to be taught as something important years ago is taken for granted that folks know to do today. And many do not wash their hands, even after going to the bathroom.
I think the other thing is courtesy. It is slightly gross when you go to grab a doorknob and it is wet and slimy. Ugh. Maybe Howard Hughes was onto something! LOL
Lastly, people something do not know their limits. A couple of years ago, I had an employee that came into work, puking and hacking like mad. I TOLD him to go home. He did not want to and I said "I'll not have you spread what you have to the rest of the staff in the suite because you are stubborn". He ended up being able to get some rest.