Traveler's diarrhea is an infection of the intestines that affects about 50% of people who visit the developing world. It comes from eating contaminated food or drinking contaminated water.
Traveler's diarrhea usually is caused by bacteria (most commonly E. coli). It also can be caused by viruses or parasites. The diarrhea is usually not serious and goes away without treatment. However, when diarrhea is very watery and occurs often, dehydration may occur. Dehydration is the biggest danger of traveler's diarrhea.