Even a child that has something and comes to care will not necessarily infect everyone else. Not all viruses are that virulent. Often I have had one of my own kids get sick and miss a couple days of school and no one else in my family or the daycare get sick and I never went overboard following them around with disinfectant either.

I tend to look at this as family care and we just care for whatever the "family" member needs that day. Having said that I use my best judgement when dealing with each situation.