Experts agree that the best thing travelers can do to reduce their chances of getting sick is to maximize their use of soap, water and hand sanitizer and minimize the number of times they touch their face.

Other tips for staying healthy include:

On the plane: Almost half the respondents to a TripAdvisor survey in April thought planes were the primary source of infection while traveling. But modern planes circulate the air about 15 to 20 times an hour through powerful filters that remove almost all contaminants.

As a rule of thumb, worry only about those two rows in front of or behind you and the sneezing, wheezing person right next to you. In that case, you might ask to be reseated or don a mask to breathe through.

Dehydration poses a greater risk, drying out the body's natural defenses against germs. Avoid coffee and alcohol, which act as diuretics, and try to drink a cup of water an hour. Saline solutions can keep your nose and eyes moist, providing a barrier against germs.

Also wipe your tray table with a disinfecting cloth, never drink the water in the lavatory and use a hand sanitizer at your seat after using the bathroom.

At the hotel: Dr. Philip M. Tierno, a microbiologist at the New York University School of Medicine, recommends setting the bedspread aside, since it is washed rarely, and making sure the sheets are crisp and clean; if they are not, request another room. Check the mattress for bedbugs. Next, wipe down the telephone, night stand, remote control and bathroom with disinfectant. Disinfect the handle on the minibar fridge. Then relax.

Out and about: Americans traveling to less-developed nations should pay special attention to the water, according to Dr. David Schlossberg, a professor of medicine at Temple University who contributed to and edited the book "Infections of Leisure."

He recommends drinking only bottled water with a sealed cap, to make sure you're not swallowing dressed-up tap water. Carbonated water is best. Do not use ice (frozen tap water), do not eat salad (washed in tap water) or fruit you can't peel yourself. Use bottled water to brush your teeth. At restaurants, he cautions against eating anything that is room temperature or seems undercooked.

"For all the advances in medicine, infectious disease remains the No. 1 killer on the planet," he said.