That's amazing Momto2! No infection for over 10 years. You should be telling us all how you do it. Do you think throwing them out so frequently is one of the reasons? One of the recommended methods is to disinfect the cups in a dishwasher that gets above 158 degrees - perhaps that's what you have. Are these disposables or reusable cups? I'm wondering how the disposables hold up in the dishwasher; they melt down and warp if you boil them.
I know all about those colds from school - it always seems like the beginning of school in particular is certain to bring home a new bug for everyone to share. Of course, for us it can last 2 months instead of 2 weeks. I wish I knew how we avoid that every year. . . .