If you feel guilty the next time you pick up the phone to take a sick day, you may be slightly comforted to know that your job might have been the source of your illness.
Whether you work in an office or in a setting where the unclean things around you are more visible, you're likely to encounter plenty of microbes in your workplace.
"One of the reasons things get so dirty and germy is that hygiene hasn't really developed this century for workers," said Charles Gerba, a microbiologist at the University of Arizona, whose work on microbes has earned him the nickname "Dr. Germ."
But while Gerba and other researchers have studied surfaces, it seems no one has ever looked at germs across all occupations.
However, he said, the move from outdoor work to offices in the 20th century not only brought us closer together, it has allowed us to share our germs even more.
"I just think that we need to develop some kind of hygiene strategy for offices," said Gerba. "The more space we share, the more germs we share in offices.
"The office environment has created a mechanism for moving germs around," he added. "You want to make sure your immune system's getting good exercise, people always say, to go work."
But avoiding the office altogether isn't going to be an improvement. Gerba has found in his studies that home offices are even germier than ones at work.
"If you don't want to be exposed to germs, don't work at home," he said.
But exposure to all of those germs may not be a bad thing.
"If you're in a totally sterile environment, your immune system doesn't get primed for where you really need it to," said Dr. Ted Palen, an internist at the University of Colorado and a researcher in the informatics department of the Colorado Permanente Medical Group.
So, being around those germs can help protect you. And while it may also be difficult to find the least germy job, Gerba has one suggestion for those who really want to escape the microbes.
"If you want to stay healthy, become the weather center guy on the North Pole," he said.
With that in mind, we give you 10 jobs where germs can be a daily concern.
When Gerba and other University of Arizona researchers studied the desks, computers and phones from various professions, teachers wrecked the curve.
Teachers had six times more germs in their workspace than accountants, the second-place finisher, with slightly cleaner desks but five-and-a-half times more germs on their phones, nearly twice as many germs on their computer mice and nearly 27 times more germs on their computer keyboards than the other professions studied.
The reason for all the germs is, of course, the reason why the teachers are there in the first place.
"Kids' desktops are really bad, too," Gerba said. "Probably the dirtiest object in a classroom is a kid's desktop."
Children hand in tests and homework papers to their teachers, and during flu season, they often hand in cold and flu germs, as well.
Of course, the germ risk teachers face may be greater because they don't walk into their classrooms wearing hazard suits.