T.S.
My youngest was a preemie so germs have always been a concern for us. I have always been scared to take him anyway with other kids, however I have learned that hand washing is the most important thing I have ever taught him. I know a sink is not always handy but keep hand sanitizer in your purse or diaper bag. Also as a member of our local Y I can tell you they are great about keeping as many germs out as possible. They have a sign on the door that asks all people entering to wash their hands first-the DC is right next to the bathroom, this last fall they installed a sanitizer dispenser outside the DC room so that it only takes a few seconds for people to clean up before entering the room. We even have one attendant that spends her own money on Lysol and sprays toys that have been in mouths and the whole room at the end of each shift, they have even put a sign up by the sign in/out sheet asking parents to donate Lysol and hand sanitizer to keep costs down and enviroment as safe as possible.
As for diarrha with RSV that is probably a side effect from getting RSV. When you have RSV your immune system is low making it easier to catch other bugs. I am guessing your son has had RSV for a few days already, while his body was fighting to help his lungs he probably got a secondary virus. just keep pushing fluids. If he hates washing his hands my son LOVES the kids antibac line from Bath and Body, they have great foaming hand sanitizers that make them smell like grape bubblegum.