Back to School Germs

I heard a lot of people this past week talking about back to school germs. At the time, we were all healthy, but things have changed. Both my 11 year old daughter and 3 year old son have colds. My 3 year old son mentioned last week that the teacher said one of the boys had a "drippy nose and mouth"(by the way, what's a drippy mouth?), so he probably got his cold from preschool. My daughter said all the kids around her have colds, and one of her teachers said it's going around. I also saw a mom on my walk this morning and she said her middle school daughter was just out with a cold and now she and her husband had it too!

That got us talking about back to school germs. My daughter was around other kids all summer at dance class, and my 3 year old was around kids in Sunday School, yet none of them got a cold until they went back to school. So, what is the difference in school? The mom I was talking to thinks it's because they're all breathing the same stale air in the classrooms and touching all the same things like doorknobs and desks. She thinks in dance, they're sweating it off, plus they don't really touch anything. So what do any of you think? Where to the back to school germs come from and have any of your children been afflicted with them?