For most of us, staring at a computer through the fog of illness is torture and does nothing to help us recover. Yet 3 million people, or 2 percent of the U.S. population, bring their ailments to work each week—a phenomenon the researchers dubbed ”contagious presenteeism.”

Many do so because of financial pressures; nearly a third of workers have no access to paid sick leave, according to the Bureau of Labor Statistics. The other two-thirds, who have the luxury of taking a sick day, need to stop making excuses for showing up at work sick.

Almost half of workers say they worry work will pile up if they stay home sick. People who find their jobs engaging also have a hard time staying home, finding work more fun than submitting to the reality of a sick day.

“Some people want to appear tough and signal that they are hard-working,” said Ziebarth.

But those diligent workers aren't just showing their commitment, they're also showering their co-workers with germs; the modern open office plan is a breeding ground for contagious illnesses. Worst of all, people tend to come to the office at the beginning of an illness, when they're at their most contagious but still feeling well enough to get a little work done.

“You have over-the-counter drugs that suppress your symptoms, but they don't suppress contagiousness,” Ziebarth pointed out.

Employers, for their part, should encourage ailing workers to stay home. Presenteeism—showing up at work ill, whether they're contagious or not—costs companies about $150 billion a year, one study estimated. A worker is about a third as productive when he's slumped in a desk chair working at half-speed as he is when he's healthy, say researchers. By staying home when he's sick, he can get better faster. The rest of the workforce can remain in full—and fully productive—health.

And diligent workers who absolutely must meet a deadline or finish a life-or-death project should at least self-quarantine. Telecommuting has become an increasingly acceptable way to work, and 60 percent of employers let employees work from home, according to the Society for Human Resource Management's annual Employee Benefits Survey.

“It's good to change the culture of how people see each other,” said Ziebarth. “You can signal hard work in a lot of different ways. It's not the right way to go into the office and spread diseases.”

In fact, we all need to do our part to stigmatize coming to work sick. If a co-worker comes in complaining of a tickle in his throat or clammy hands, say: “Go home! Nobody wants you and your gross germs.”

Or just send him a link to this article.

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