Travelers need to exercise caution.

• Position: Contagious Diseases

Brent W. Laartz thought he was in for the times of his life when he set out on a horseback riding excursion in Costa Rica. Admittedly younger and more naive than he is today, Laartz--an infectious disease specialist and author of How to Avoid Contagious Diseases-- failed to take some of the precautions necessary to avoid becoming one of the 40% of travelers every year who bring back an unwanted souvenir from their trip abroad: an illness. "While on any International vacation, it becomes entirely necessary to be more observant of the conditions that are in place that could harm you."

Laartz offers tips on how to protect yourself on your next trip and to make sure the ride of a lifetime does not turn into the worst ride of your life:

* Avoid local water in all forms. When you shower, do not ingest the water and do not be afraid to ask for a drink without ice. In lesser-developed countries there is less infrastructure for clean water, effective sewage, and public health. If you cannot avoid unsanitary water, make sure you have iodine tablets and bring along a tea- or coffeemaking device that will boil water for you. Furthermore, you should buy a case or two of water when you arrive at a destination and check that all bottle caps are sealed to assure the water Is not just a refilled bottle of dirty, parasite-infested tap water.

* Protect your feet at all times. Use flip-flops in the shower and, if you must be barefoot, put a towel...