(Well, duh! Any parent or teacher could have told you that without conducting a four-year study. But I digress.)
So. How do you keep your little bundle of happiness from spreading those little bundles of disease around your house?
Two little words. Fear and brainwashing.
Start by instilling fear. Explain to your children what germs are, how they are spread, and what havoc they can wreak on their little bodies. Paint a mental picture for them that is so vivid and appalling that their eyes widen in shock.
Then begin the brainwashing. Every time your children come out of the bathroom, bark "Did you wash your hands?". Your child will lie and say that he did. Say "Go back in and do it again. AND USE LOTS OF SOAP!!!" This should happen at least 4-5 times a day. When your children arrive home from school, do not greet them with a smile and a hug. Cut off their excited cries of "Hi, Mommy!" with a curt "take off your shoes and wash your hands, and then you can come talk to me." Phrases like "change your shirt, it's dirty", "did you brush your teeth? No, really, did you?" and "when was the last time you washed your face?" should be flung at your children throughout the day.
At first, your mother, your sister, and your neighbor will be appalled at the way that you are speaking to your children. The children themselves will be tense and confused. After a few weeks, however, your kids will see that you mean business and will begin to wash their hands (with soap!), brush their teeth (with toothpaste!), and remove their shoes at the door without being told to. As these habits become ingrained, you can ease up a bit, and your children will gradually forget your fascist behavior and will grow to love you again.
It's a win-win situation for all.
If you start now, perhaps you can avoid having the flu hit your house this winter.