Wow, most of you guys have understanding places of employment. If I don't go to work - sick or not - others have to pick up my slack. They'd rather me come in sick. (I don't ride my bike, though. Might start, after reading these comments.)
They are stupid. If you get a cold, that's one unit of slack to be picked up. On the average, you can spread it to 5 people, that's 6 units of slack to be picked up. Do the math.