Because of things like this diarrhea problem (which can sometimes be quite severe) in the last decade combat wounds and injuries have been very much a minority of casualties in the combat zone. For example, during the first year of fighting in Iraq (2003-4) 2,998 soldiers were killed or wounded in action, while 18,004 were evacuated from Iraq for other medical conditions (accidents and mostly disease, including severe diarrhea). The U.S. has known since World War II that areas like Iraq are full of strange (to Americans) and debilitating diseases. Efforts to find cures for a lot of these problems is hampered by the fact that few people (mostly foreigners) suffer from them and developing a cure is expensive and not justified by the small number (even including military victims) involved. Modern medicine can do wonderful things, as long as you have someone willing to put up the vast sums (often several billion dollars) to develop a safe and effective cure.