As the weather turns cooler and people stay inside more in closer quarters, an unwelcome guest is starting to appear: the flu.

So don’t mess around. If you haven’t already gotten the flu shot, please get it now.

The Maryland Department of Health reports 11 cases in the state already, so the season has begun. According to the Centers for Disease Control and Prevention, two variants of influenza are expected to be in force this fall and winter: the H1N1 and the more severe H3N2 (known for its evasive maneuvering and mutations).

Neither would be a picnic. And of course, it’s cold comfort that medical officials remind Americans that the flu shot isn’t completely effective this year, or any year. Scientists have to guess which flu virus or viruses will be most prevalent, and they often guess at least partly wrong. The flu is a wily foe. But it’s still better to have a shot and be reasonably secure rather than to roll the dice by doing nothing.

Every year, so many of us fail to heed medical advice to get the shot, coming from the CDC as well as local sources like Charles County Health Officer Dr. Suzan Lowry. Excuses abound, but none of them are good. If avoiding the nasty symptoms of the flu isn’t enough incentive for you to get the shot, then consider this: Taking the shot doesn’t merely immunize you against the flu. It also inoculates you from all those smug know-it-alls whose first remark upon learning of your misery is always the same: “Too bad you didn’t get the flu shot.”

But if you do get sick, you definitely shouldn’t drag your flu-ridden carcass into the office, expecting to be welcomed as a noble comrade who soldiers on even with a fever, cold sweats and uncontrolled coughing. Forget it. Anyone who comes to the office with the flu, spreading germs in his or her wake, should be treated as a pariah to be quarantined. The sufferer immediately forfeits any claim of superiority.

The flu spreads because people spread it — on a micro level — when they’re sick. A couple of years back, scientists from the Massachusetts Institute of Technology studied sneeze dynamics and droplet formation. Their aim was to thwart epidemics and solve the mystery of why some people spread infection via sneeze more effectively than others. Here’s what they found: In enclosed spaces, like an office, or a public transit bus, a sneeze that doesn’t get expelled into a tissue (or into the crook of your arm, which always better than in your hands) releases mushroom clouds of germs that within minutes can reach ceiling height and cover the entire area.

There’s a lovely picture for you.

Every boss, every co-worker, should deliver the same message to flu sufferers: Thanks, but you aren’t that important. We can get along for a few days without you. Or consider this: If you infect your office mates, you’ll be the one doing their work when you’re back on duty and they’re still home in bed, suffering and blaming you. In other words, it’s a lose-lose situation. And parents should keep sick kids out of school as a show of common sense for all involved.

So get the flu shot. And if you get sick, stay home. To everyone else, good luck. And keep washing your hands.

The Charles County Health Department accepts walk-ins for a shot Monday through Friday from 8 a.m. to 4 p.m. at its White Plains office at 4545 Crain Highway. The next free outreach flu shot clinic is Thursday, Nov. 7, from 4 to 7 p.m. at Smallwood Middle School, 4990 Indian Head Highway.