Surfaces that other people have touched can be pretty dirty. Each person who touches a surface, whether it’s a doorknob or a keyboard, leaves their own microbial mark. A new study out this week set out to figure out just how fast these germs could spread within an office space given a single source of contamination.

The group used a tracer virus whose presence could easily be detected. Researchers seeded it on to a doorknob in an 80-person office building. They then waited four hours before testing a variety of surfaces, including the hands of all employees, to see how far the virus had spread.

The researchers found that within four hours the virus was already present on half of individuals tested in the building. It was also found on a majority of commonly touched surfaces like light switches, computers and phones. The study also found that the break room was a big hot spot for virus spread, because most members of an office visit it frequently. As the authors point out, many people start their workday by grabbing a cup of coffee. This makes the coffee pot a prime location for both dropping off and picking up unwanted passengers on our hands.

The study comes on the heels of the recent outbreak of enterovirus D68 that has caused respiratory illness and hospitalization of more than 1,000 children in the South and Midwest. Enterovirus is an exceedingly common type of virus that most often causes the common cold, but can cause more serious illness depending on the species and strain.

These viruses are passed through contact when virus present on one surface is transmitted to a person’s body through their mouth, often during one of the three to four times per minute that a person touches their face. The best way to stop these viruses is to wash your hands frequently for 20-30 seconds in warm water with soap. When you’re away from a bathroom, hand sanitizer and disinfecting wipes can also significantly reduce viral spread.

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