"[In countries with poor sanitation] be very careful of water and things washed in water," Rosenthal says, referring to foreign countries where the water supply contains levels and types of bacteria different than in the U.S.

These bacteria can often make unaccustomed Americans sick, causing diarrhea and other ailments.

Worm infestations are also a problem for individuals who go barefoot or eat food that is not thoroughly cooked. Many worms can thrive in an individual's intestinal tract and significantly limit that person's nutritional intake.

Rosenthal says travelers should also be concerned about purchasing antibiotics in some developing nations.

Sometimes, he said, because of poor public health regulation, travelers are given incorrect doses of antibiotics. Improper doses are dangerous when they reduce the normal levels of bacteria in the body, which allows other bacteria to reproduce and cause harm.

"Some students developed aplastic anemia when they were given harmful antibiotics for minor illnesses," Rosenthal says, describing a severe case faulty antibiotic use abroad.

Aplastic anemia, which can be fatal, is a failure of the bone marrow to produce normal blood cells.

UHS, in its soon-to-be-released guidebook entitled Healthy Travel, recommends inoculations or oral vaccines against the following: poliomyelitis, tetanus, diphtheria, typhoid fever, viral hepatitis, pneumococcal bacteria, influenza and meningococcal bacteria. The new guide also recommends the updating of childhood inoculations against measles, mumps and rubella.