[header] How to prevent traveler's diarrhea [title] Avoid drinking the tap water in developing countries. [step] The tap water in developing countries in central and south america, the middle east, africa, and asia may be contaminated with bacteria, parasites, and viruses. These can all cause traveler's diarrhea (td). 
When visiting these areas, only drink sealed, bottled beverages like bottled water, tea, soda, beer, wine, juice, and coffee. [substeps] If the seal has been broken, choose or ask for another bottle.