Millions of people will hit the roads, rails and sky this holiday season, and tagging along with them will be hordes of germs ready to spread to the traveling masses.
Despite being surrounded by bacteria and viruses in stores, airports and other public places, there are a few simple ways to minimize the risk of catching a disease, such as the cold and the flu, which could zap the happy out of the holidays.
"You don't want to be a hermit, and you want to enjoy the holidays, but try to use some common sense principles to avoid getting sick," said Dr. Lisa Bernstein, associate professor of medicine at Emory University School of Medicine.
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In an effort to help spread healthy holiday cheer, Bernstein and other doctors share the following tips for fending off germs while traveling:
It's the No. 1 rule that experts repeat over and over (and over) again: Wash hands.
"You're constantly touching surfaces that people have sneezed and coughed on, and then because you're in a crowded airport or on a plane you may get hot or sweaty, you wipe your eyes, nose or mouth and can spread germs," said Dr. Michael Perskin, assistant professor of medicine at NYU Langone Medical Center.
Soap and water aren't always available, so alcohol-based hand sanitizers are essential travel items.
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"Liberal and frequent use of alcohol hand rubs is very important," said Dr. Laurence Gardner, professor of medicine and executive dean for clinical affairs at the University of Miami Miller School of Medicine. "If I were really concerned about acquiring a cold or a respiratory infection, I would apply that to my hands every 30 minutes or when I used the bathroom or touched any other surface."
"Wash kids' hands often as well, and encourage them to use a tissue and sneeze or cough into their elbow," said Bernstein.
Of course handwashing doesn't only apply to sitting on airplanes. With a much greater volume of people and germs in stores and other places, disinfecting hands, shopping carts, seats is extremely important.
Airplanes are notoriously germy places. Studies have shown that airplane bathrooms harbor a number of different types of bacteria and viruses, and the recirculated air in planes can also contain many infectious agents. Germs also lurk on tray tables and on seats and seat backs.
"If you're in a plane, wipe down seats, seat backs and tray tables," said Bernstein. Travelers should also, as always, wash their hands whenever possible.
A 2009 study by the U.S. Centers for Disease Control and Prevention found that passengers on two lengthy flights into Australia were at increased risk for getting a flu-like illness after the flight if they sat up to two rows away from a person who had flu symptoms before the flight. They were at even higher risk if a symptomatic passenger sat within two seats in front, behind or to the side.
While it may be difficult to control who sits in nearby seats or rows, if a person is sneezing or coughing, try to stay away from that person and disinfect surfaces and hands regularly.
"Also, don't touch your eyes, mouth or nose, since there are only so many times you may be able to wash your hands," said Perskin.
Spreading germs is a two-way street, so people who may be coughing or sneezing should be careful to avoid coughing or sneezing into other people's faces and should use tissues or hold their mouths when possible. They should also, of course, wash their hands.
Proper nutrition and physical activity are important all year round, but especially during the holidays. People may neglect these needs because of bad weather or other obligations, but they are vital to staying healthy.
"Eat a healthy diet and exercise -- those are the best preventive activities along with not smoking," said Perskin. "Your immune system will be healthier and that will help fight off infection."
"Even though it's December, it's not too late to get a flu shot. Flu season goes through early spring," said Bernstein.
"This is the prime time for influenza," said Gardner. "When peole are in enclosed spaces in cold environments, the passage of viruses -- especially the flu virus -- is much greater than in wide open spaces in the summer."
Perskin also suggests getting vaccinated against other disease, such as whooping cough, or pertussis.
Although it may seem inconvenient to worry about flu shots on top of everything else, the alternative could be a lot worse.
"It would be an enormous waste of time if, because of not getting vaccinated, someone spent five days in bed with a fever and just felt crummy," Gardner said.
A version of this story previously appeared on ABCNews.com.