How Quickly Do Germs Spread in the Office?

We’ve all done it. Come to work when we’re sick.

We know we’re not doing our fellow workers any favors by exposing them to whatever we’ve got, but pressure to get our jobs done almost always trumps common sense.

Well, now there is research to back up what common sense has been telling us all along: It’s a bad idea.

Environmental microbiologist Kelly Reynolds at the University of Arizona in Tucson noticed the trend in her own office. As winter wore on, more and more of her colleagues started feeling ill. “So we asked the obvious question: how well do germs spread if one person comes to work sick?” she said.

So Reynolds and her team launched a study in one of the University of Arizona offices involving a typical cast of winter characters: several dozen coworkers in good health and one “sick” colleague carrying a virus mimicking the flu.

Within four hours, more than 50 percent of surfaces and employees were contaminated with the virus. Pretty startling stuff.

We spoke with Reynolds recently to learn more about her experiment.

NEWSHOUR: Kelly, thank you so much for joining us. Anyone who has worked in an office has had suspicions about how quickly germs spread in an office but your study puts a time stamp on it. Tell us how you came to these conclusions.

KELLY REYNOLDS: Well we targeted an office building of 80 people and we asked 10 of those people to volunteer to be “artificially inoculated” with a surrogate virus. These are viruses we know infect bacteria — not infect humans — but they have very similar survival and spread tendencies as influenza and other viruses that we know cause disease in humans. And so we put droplets of water on their hands, and one of those drops of water, unbeknownst to the participant, had this surrogate virus present in the droplet.

The level of virus in that droplet simulated what you’d expect on a person’s hands if they were sick. We then asked them to go about their workday. And by noon — four hours into the workday — we went and swabbed commonly used surfaces in that office building and sampled the hands of all the coworkers. Half of those surfaces and half of the hands of the coworkers tested positive for the virus that we planted.

NEWSHOUR: That’s pretty quick. Is it what you expected?

KELLY REYNOLDS: I was very surprised at how effectively our virus spread. Because in the office building we targeted, people tended to stay in their cubicals or in their offices the majority of the day. There was very little social interaction. It seemed like people were very isolated in their offices. But throughout the day, everybody tended to go to the bathroom at least once and they tended to touch one of the common areas.

NEWSHOUR: Which common areas?

KELLY REYNOLDS: We were targeting surfaces that we know are commonly touched but maybe rarely disinfected — things like the computer keyboard, the computer mouse, the desktop in front of an individual’s workspace. But then we also went into the common areas of the office building and tested the coffee pot, the refrigerator handle, a copy machine that an entire floor shared, doorknobs, faucets in the bathrooms.

NEWSHOUR: Were there different types of bugs that lasted longer on these surfaces?

KELLY REYNOLDS: We were only looking for the bug that we planted. In the real world, different pathogens survive at different rates. Probably the maximum survival rate is three days, and the minimum is a couple of hours. If it’s a metal surface, they only survive for hours. If it’s a plastic surface, they tend to survive much longer. If it’s a porous surface, you know some plastics have little grooves in it — if there’s more organic matter, more dirt, then that’s protective for the organism. The influenza and cold viruses can survive up to three days on surfaces.

NEWSHOUR: We always hear about things we can do to prevent the spread of germs in the workplace — the No. 1 being stay home. But what about simpler steps, like washing your hands and using hand sanitizer, how effective did you find those to be?

KELLY REYNOLDS: We put together for this study what we called the ‘healthy workplace interventions,’ which had three parts:

The first was providing tissues to the employees, so if they had to blow their nose or cough, they used a tissue rather than their hands.

The second part was to provide hand sanitizer at each individual’s desk that they could use throughout the day. We didn’t really tell them how often to use it — we just asked them to be aware when they think they come in contact with somebody or something that’s contaminated, like the bathroom.

And then we asked them also to use disinfecting wipes. We provided a bottle of disinfecting wipes and asked them to use them at least twice a day. So maybe when they first got into work, and then maybe right before they ate lunch at their desk, or at the end of the day before they left.

We didn’t monitor any of that, we just gave that advice and asked people to do that. And so after we gave people a couple of days to get used to the ‘healthy workplace interventions,’ we repeated the study by inoculating a single person’s hands and watched how the virus spread. And we found that the risk of infection from exposure to contaminated surfaces and other people’s hands was reduced by up to 90 percent.

NEWSHOUR: You also studied the behaviors that spread germs fastest. What did you find?

KELLY REYNOLDS: It tends to be a general perception that people are worried when somebody in their vicinity sneezes or coughs. And certainly this is a mechanism for germs to be transmitted in the environment. But it’s much more likely that you’ll come into contact with somebody else’s germs from a contaminated surface, because the viruses in aerosols just don’t stay in the air very long. They tend to settle on surfaces. And that’s where they survive for hours to days. And so you’re much more likely to pick up a germ from where that person has coughed even though you don’t even realize you’ve come into contact. And that’s why it’s important to have these ‘healthy workplace interventions’ in place all the time.

The other thing to be aware of is how often you touch your face with hands that may not be clean. We tend to have a habit of wiping our noses, or rubbing our eyes, and the eyes, nose and mouth are entry routes into the body for germs. So be careful not to touch your eyes, nose or mouth when you know you haven’t washed your hands recently.

NEWSHOUR: How much does environment play into this? Does the office set-up have a role?

KELLY REYNOLDS: I think so. As a population, we have moved further away from people living in rural environments and people are coming together in higher populations in city settings. And so there’s obviously more industry, more opportunities to work in these large office buildings. And we just tend to come into more contact with more people more often.

So we’ve moved away from being farmers out in the field and shopping at our local markets for local produce and supplies to really having a global food supply. There’s also lots of travel happening, so you could come into contact with anybody in the world in a very short period of time. So we have a much higher increase in interaction and a complete change toward more than an urban system, where we are in much closer proximity to one another.

NEWSHOUR: After your study, have people changed their behavior at your own workplace?

KELLY REYNOLDS: Yes they have. But I have gone around the workplace and said to people, “Those are the same disinfecting wipes that I gave you. I think it’s time to use those up and get some new ones.” That’s another issue — when we get a little too lazy about things, we forget. I think that’s something employers can really do: remind your employees, send an email out once in awhile. Use these products that we know are effective, and stay home when you’re sick.

One of the things about the flu is that you could be shedding the virus, you could be contagious before you’ve even experienced symptoms. And even when your symptoms stop, after five days of the flu, you can still be contagious and not even realize it. You may feel like you can go back to work, your symptoms have subsided, but you could still be contagious to your coworkers. In that way, it’s not necessarily the responsibility of the person who’s sick — it’s the responsibility of everybody else to make sure they’re following these protocols, as well.

NEWSHOUR: It’s a very interesting study. Kelly Reynolds, thank you so much for joining us.


This conversation has been lightly edited for clarity. Top photo by RubberBall Productions/Getty Images.