Hi M.,
I am not concerned because my children are pretty healthy. When they do get sick, it isn't for long. Those who need to be the most concerned are those who have children who are constantly getting ill, have a medical condition that causes them to be ill most of the year or all of the time.
In my house, to start with, we all use our own toothpaste. Sick people do not share hand towels with well people and are encouraged to wash their hands often.
I have on hand electrolyte drinks (Pedialite, coconut juice, you can also make your own homemade electrolyte drink - there's a recipe on the web), Tylenol Meltaways, and ice packs in the freezer. That way, should anyone get sick, I have the supplies I need and don't have to run out of the house to get them if someone becomes ill.
I always encourage hand washing. Be sure to use lotion after washing! Dry skin harbors germs! They live in the cracks. Wash up and use lotion. Next time you wash your hands, you know you've done a good job washing when you feel the lotion wash off.
Keep your home hydrated. We use humidifiers during the winter. Germs survive better in dry conditions, so I've heard on the news. If there is water condensation, turn off the humidifier until they dry off. Too much humidity allows mold to grow - that just causes another health concern!
: ) Maureen