Erik Witsoe/EyeEm via Getty Images We're surrounded by bacteria and viruses every day, but there are some germy places in the airport and on flights that might make you extra cautious.

Considering the millions of people who move about in airports and on airplanes every day, it’s no surprise that these travel hubs may make you a bit more cautious about germs.

Most germs you come across every day aren’t dangerous unless you have an immune deficiency or an open wound. Bacteria and viruses surround us, and many are harmless. But there are some spots that lots of people come into contact with that you might want to keep in mind while traveling, just to be safe.

We rounded up a few studies and experiments to point out four germy spots in airports and on flights that you might want to give a quick wipe-down before touching. Check them out below.

The Tray Table

In 2015, travel calculation site Travel Math sent a microbiologist to collect 26 samples from different surfaces in five airports and on four flights. The tray table on the back of cabin seats tested highest for bacteria, with 2,155 colony-forming units per square inch.

For reference, the lavatory flush button had 265 colony-forming units per square inch. Another spot that beat out the flush button? The overhead air vents, which had 285 colony-forming units per square inch.

The microbiologist from the Travel Math study did find that all 26 samples tested negative for fecal coliforms like E. coli. However, in a 2017 interview with Time, Dr. Charles Gerba, a professor of microbiology at the University of Arizona, said he’s tested tray tables on flights that hosted cold viruses, norovirus and the bacteria MRSA.

Water Fountain Buttons

Travel Math found that in the airport, water fountain buttons took the crown for the germiest spot, with 1,240 colony-forming units per square inch, while the bathroom stall locks tested for a surprising 70 colony-forming units per square inch. The Travel Math team pointed out that this may be a result of cleaning crews having regular cleaning schedules for bathrooms (for good reason), but not other areas, such as the water fountain.

In 2012, Gerba showed how germy water fountains can be in a study in which he partnered with Kimberly-Clark Professional and The Healthy Workplace Project to test samples from office buildings. They found that 23 percent of the water fountain buttons tested had high levels of adenosine triphosphate, or ATP, a molecule helpful for testing for contamination.

Your Seat On The Plane

In 2014, researchers from Auburn University proved in a two-year study that bacteria can thrive on flights for several days. A major airline carrier sent researchers material from common items such as window shades, plastic tray tables and seat pockets, which researchers first sterilized before adding bacteria like MRSA and E. coli. The researchers simulated temperature and humidity levels common on a commercial flight to see how long the bacteria would survive.

The bacteria lived the longest on cabin seat material. MRSA survived for 168 hours, or seven days, on the seat-back pocket material, and E. coli lived for 96 hours, or four days, on the armrest material. The research was not meant to be “alarmist,” the team noted, but a helpful resource for airlines.

TSA Bins

In 2014, journalist Jeff Rossen and his investigative team took samples of surfaces in airports and planes as they hopped on three cross-country flights on different major airlines. Tested by microbiologists, the samples showed that TSA bins are particularly germy. One of them tested positive for “fecal matter at levels high enough to make people sick.” This isn’t all that surprising, considering people place their shoes in the bins.

Akron-Canton Airport in Ohio started combating the spread of bacteria in TSA bins in September 2017 by partnering with a local hospital to use trays lined with self-cleaning orange mats and handles.

It’s important to remember that there is room for error in studies and experiments and that many airports are already revamping their cleaning to-do lists, as USA Today reported, to include automatic floor-scrubbing machines and frequent wipe-downs of kiosks.

The reason bacteria may last so long on flights is because some cleaning crews don’t get enough time to properly sanitize the cabin. In February, The New York Times interviewed a cleaning crew member who said the workers have limited time to clean the plane before more passengers hop on.

“To clean, we need 10 to 15 minutes, but they give us seven or six,” said Sameer Yousef, who at the time was a lead cabin cleaner for a team that cleaned airplanes from United. “It’s a very big pressure for us. They don’t give us more people to help.”