Diarrhea is a loosening of the stool. Dysentery is the same, with the addition of blood. Either of these conditions can be caused by bacteria, virus, or parasite. If untreated, either of these could be fatal over a period of several weeks. Prevention is the best course of action. Mix up a disinfecting solution of bleach or iodine and water for use after a crisis. Place 20 drops of tincture of iodine 2% in one quart of water. It doesn't matter if the water was potable, as the high level of iodine will disinfect it within minutes. Wipe down all surfaces that could transmit pathogens, especially around the latrine area. A similar wash can be made from 10 drops of bleach in one quart of water. Make sure that dishes and hands are adequately washed during your emergency situation, and that only safe foods and drinks are consumed. If you try to wash clothing, use scalding hot water for an initial soak to disinfect the fabrics.