Causes

It's possible that traveler's diarrhea may stem from the stress of traveling or a change in diet. But usually infectious agents — such as bacteria, viruses or parasites — are to blame. You typically develop traveler's diarrhea after ingesting food or water contaminated with organisms from feces.

So why aren't natives of high-risk countries affected in the same way? Often their bodies have become accustomed to the bacteria and have developed immunity to them.