Every worker has been there. Before you open your eyes, you know you’re sick. Your head is pounding, your nose is stuffed, and every muscle in your body aches. You think you have a fever and even suspect the flu. But you’re a dedicated employee, so you tough it out and head in to the office--after all, you’ve got work to do, and you don’t want to leave your colleagues in the lurch. However well intentioned, this is a huge mistake.