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How to know if you’re contagious with a cold or flu, and when to return to work

(Photo credit: iStock/PeopleImages)

It’s an all-too-common sight during cold and flu season: sniffly, miserable people dragging themselves in to the office when they should be recovering at home. But how do you know when you’re no longer a contagious hazard to your coworkers? Read on to find out why your runny nose may mean that you should stay quarantined.

Symptom: Fever

One of the most reliable signs that you’re still a walking germ factory is an elevated temperature. As the flu virus replicates in your bloodstream your immune system kicks into high gear, releasing chemicals called pyrogens that signal your brain to raise the thermostat. This boosts your immune function and creates a hostile environment for bugs, but decreases once there are fewer invaders to fight off.

When to return: You’re less contagious once you’ve been fever-free for 24 hours, so wait at least one more day before you return to the office.

Symptom: Runny nose

All it takes is one lonely virus particle to launch a cold through your unsuspecting eyes, nose or mouth. The dreaded drip occurs when your body increases mucus production to flush out said virus, typically resolving once you’ve fought it off. Unfortunately, sometimes the inflammatory process takes longer to wind down, leaving you with ongoing dripping after the bug is gone.

When to return: If your cold started more than a week ago, the chances of infecting your coworkers with your faucet-like nose are lower — but consider visiting your doctor if things don’t improve within a couple of weeks.

Symptom: Feeling worse overnight

If a rough night after improved daytime symptoms is tempting you to call in sick the next morning, keep in mind that this pattern is part of your body’s natural cycle. While you’re resting in the wee hours the virus-fighting arm of your immune system also takes a break — leading to temporarily worse inflammation and overall misery.

When to return: If you’re only feeling rotten at night then you’re probably on the mend. Head back to work if you’re feeling up to it.

Symptom: Cough

Nothing guarantees you more dirty looks when you’re sick than a hacking cough, and for good reason — droplet spray is one of the most effective strategies a virus has to spread itself far and wide. That said, a cough can persist long after the infectious period has passed for several reasons, including airway-irritating post-nasal drip, leftover lung inflammation and overstimulated nerve pathways.

When to return: If a dry cough lingers after all your other symptoms have resolved then you’re probably germ free. Do visit your doctor to rule out other causes if it’s not clearing up over the next few weeks, however.

Symptom: Diarrhea

Although you can catch a stomach bug any time of year, Norovirus, the most common culprit, tends to peak in the winter. Diarrhea happens when your gut gets overwhelmed by viral toxins that attack your intestinal lining, interfere with digestion and increase fluid secretion. And if you’ve ever come down with stomach flu, it’s quite likely that you caught it via the fecal-oral route — which is just as delightful as the term would suggest.

When to return: Don’t even think about going to work if you’ve got the runs, because viral gastroenteritis is incredibly contagious. Keep in mind that you can remain infectious for up to two weeks after your symptoms clear, so be meticulous with your hand hygiene once you’re back.

The doctor’s notes

While it’s possible to shed some viruses for weeks or even months after initial infection, the average person stays contagious for up to a week after symptoms develop. If you absolutely must make an appearance at the office during this time, follow these tips to reduce your chances of starting an epidemic.

  1. Keep your distance from your coworkers. Research shows that flu viruses hover in the air as far as six feet away from infected hosts.
  2. Touch as little as possible. A recent study showed that one sick worker can contaminate more than half of commonly touched office surfaces by lunchtime.
  3. Wash your hands frequently with plain old soap and water. Recent evidence suggests that alcohol-based hand sanitizer may not be as effective at reducing virus transmission outside of hospitals.