First, the good news. This year's flu season may be on the decline. According to the Gallup-Healthways Well-Being Index, an average of 3.3% of U.S. people reported being sick with the flu during January. This is a drop from the 4.0% who claimed to have the flu in December, and lower than the flu statistics during January over the last two years. But that doesn't mean we're out of the woods just yet. Colds are still high, with 11.9% of Americans reporting being sick this January, up from 11.6% in December.

The first line of defense is yourself. You've read (or plan to read now that we're reminding you about it) our 26 Ways to Avoid Getting Sick This Winter. And at your workplace, you're careful not to touch, or at least wash your hands every time you touch, one of the 6 Dirtiest Places in Your Office. But what about the things you don't have any control of?

Like, say, a co-worker who doesn't wash his hands after going to the bathroom.

So the question isn't if you should address him but how, says Richie Frieman, an expert on manners and the author of Reply All ... and Other Ways to Tank Your Career. For a hands-off approach, just ask HR to send out an office memo, or post signs or comics near the urinals and sinks about hand-washing etiquette.

"Comedy downgrades the situation and makes people feel more comfortable talking about it," Frieman says.

But if you have no qualms about asking this slob to clean up his act, be sure to mention it privately so he isn't embarrassed in front of an audience. And spare the guy's feelings by keeping it casual and brief. "You don't want to make the person sound dirty and disgusting ... even if he is," says Frieman.