What causes traveler's diarrhea?

People get traveler's diarrhea by eating food and drinking water that contain germs. People can get this illness in areas of the world where the drinking water is not clean.

People who live these areas often drink tap water that contains these germs, but they do not get diarrhea. This is because their bodies are used to the germs. In the same way, cooks and food handlers may have the germs that cause traveler's diarrhea on their hands, but they may not get sick themselves. When people travel to a new place, they are more likely to become sick, because they lack protective antibodies (infection-fighting agents in the blood) that attack these germs.