-- The current flu epidemic wreaking havoc across the nation was in part fanned by so many people spreading germs while traveling over the holidays, according to the U.S. Centers for Disease Control and prevention.
As 49 states are reporting widespread flu activity, "Good Morning America" spoke with a flight attendant and a doctor to get some expert tips on how to prevent the spread of flu germs while traveling on airplanes or passing through major airports.
1. Wipe down communal surfaces such as tray tables and armrests
Dr. Nicholas Testa said that you should be wary of the communal hard surfaces on airplanes, such as tray tables or armrests.
"The flu virus will live on a hard surface for about 24 hours," Testa said.
"They don’t have time to wipe every single tray station," he added. "So intrinsically the bathroom is cleaner than out here."
A number of major carriers told ABC News that they clean tray tables and other hard surfaces in coach every night, but not always between flights.
Val Halili, a flight attendant, told ABC News that when it comes to preventing the spread of germs in the air "a lot of it is on you."
"I wash my hands at every opportunity," Halili added.
2. Turn on your air vent
The air on most planes is circulated through a system that filters it from ceiling to floor every two minutes.
If one person with the flu sneezes, the germs can quickly spread through the air directly toward the passengers seated behind or to the side of that person, according to a simulation done by the magazine Popular Science.
“You can turn your air on overhead,” Testa said, adding that this “will increase the circulation of air in front of you.”
3. Let other passengers board first
It is not just aboard airplanes that travelers should be cautious of flu germs. Thousands of passengers also pass through major airports across the country every day, standing close together in tightly packed lines.
Testa also advises travelers to be patient when it comes to boarding a plane if you want to prevent the spread of flu germs.
"All those people are clotted together in the boarding process; it’s far more likely that they’re going transmit a virus to each other," Testa said. "Just let the other people board. And give yourself a moment."
4. Choose a window seat
When it comes to where to sit onboard, Testa recommends choosing the window seat, saying it "has less traffic by it."
This means less potentially infectious people will have touched your armrest or headrest while walking through the cabin.
5. Avoid caffeine, alcohol while aboard
Testa also recommends avoiding drinking caffeine or alcohol while flying if you don’t want to get sick.
"Both of those are shown to increase your dehydration and decrease your immune system," he said.
6. Use a nasal spray
Halili said a pro tip he recommends is to use nasal spray, which he says he pumps "every two hours" while flying.
Testa said using nasal spray "keeps your mucous membranes moist."
"One of the things we’ve noticed, particularly on airplanes, is that as soon as your mucous membranes, particularly in your nose and your mouth, start to dry out, we lose one of the most valuable defenses for preventing respiratory viruses," he added.
If you do have the flu and can't travel, some airlines say that with a doctor's note and on a case-by-case basis, they may let you cancel your flight and give you the value of your ticket toward future travel, but it is best to call your airline and ask their specific policies.