Some vaccines must be given in a series over several days or weeks. You should see your doctor as early as possible before your departure to find out what medications or vaccines are recommended and allow enough time for them to be given.

Hepatitis A can be contracted anywhere, including the U.S. But infection is less likely in Western Europe than in less developed countries. Vaccination is not recommended for travel to Western Europe.

If you can, walk up and down the aisle of the plane. If traveling by bus or train, make the same effort. If traveling by car, stop and walk around every hour or so, the National Heart, Lung, and Blood Institute says. While seated, you can move your legs and stretch and flex your feet, which improves blood flow in your calves. Movement prevents blood from pooling. Wearing loose, comfortable clothing and drinking plenty of fluids can also reduce the risk of developing a blood clot.

The best choice is the U.S. Embassy. Embassy staff can recommend English-speaking doctors or the best hospital in your locale.

Choose water over the other beverages listed. Caffeinated and alcoholic beverages dehydrate the body by speeding up the rate of urination. For optimum rehydration, drink one cup of water for each hour of flight time.

If you are in an area where water may be contaminated, don't use ice in your beverage, because the ice may be contaminated. It's safest to drink directly from the bottle or can, rather than from a glass, the CDC says. Also be careful of water on the outside of the bottle or can. Wipe the bottle or can dry before opening, and clean the area where your mouth will touch.

Avoid uncooked vegetables and moist dishes such as rice that could have been sitting at room temperature.

Keep any medications in their original bottles and carry a copy of your prescriptions, along with a note from your doctor if you take controlled substances.