Traveler's diarrhea is an illness that affects 20-50% of travelers from developed countries who go to developing ones. People travelling from developing to developed countries rarely get it. It is defined as two or more loose stools in a 24-hour period, accompanied by stomach cramps, nausea or vomiting. The term "dysentery" simply refers to the more severe cases, usually much more prolonged and with blood and mucus in the stools.
Traveler's diarrhea usually develops on the third or fourth day of a trip and lasts 36-48 hours if untreated, 24-36 hours if treated. It becomes more common the longer one stays in a developing country, or if the stay is in the tropics, especially in rural areas. Despite all the warnings against "drinking the water", it is actually much more likely to be spread by contaminated food. The most common cause is bacteria but viruses and parasites also play a part. So do simple things like jet lag, fatigue and a change of environment. The more severe cases (dysentery) are apt to show up later, even after the trip is over, and are more commonly from the non-bacterial causes such as giardia and amoebas or something like typhoid.
"Tourista" is actually caused by a wide range of bacteria and viruses. Most of these are killed by the acid in the stomach. The higher the "dose" of germs, therefore, the greater the severity of the diarrhea. And if those germs happen to be typhoid or cholera germs, that can be quite serious. The usual dietary precautions often do not prevent "tourista". They do, however, reduce its severity so that one can stay out of the hospital or the clutches of a doctor while his body gradually builds up immunity. The corollary of this, of course, is that anything that decreases gastric acidity (antacids, Pepsid, gastric surgery, etc.) actually may increase the risk of a severe case of traveler's diarrhea.
Because all of the treatment methods have some associated dangers and side effects, the experts agree that the best treatment is prevention. Frequent hand-washing helps more than people realize. Avoid fruit and vegetables which cannot be peeled. Cooked foods should be served and eaten hot. Buffets, sometimes even on cruise ships, are notorious for their bacterial content. And food from street vendors is anathema. Water should be boiled or bottled, not just heated (look out for pre-opened bottles which may just contain tap water.) There are filters and resins which are almost as effective and chemical treatments help some (see our catalog) but nothing is as effective as boiling. Alcoholic beverages straight from the bottle are safe but it is a myth that alcohol kills the bacteria in ice cubes. (Alcohol does kill germs--but only after 24 hours, by which time I would presume the ice has melted!)
The main problem with the diarrhea, other than the discomfort and inconvenience, is dehydration. There are a number of oral rehydration mixtures commercially available (see our catalog) but simple rehydration with flavored mineral water or soft drinks is usually adequate in adults (the sugar and salts in them are as important as the liquid.) Avoiding milk products is usually recommended but not of proven benefit. Children get dehydrated faster than adults so might be good candidates for the commercial mixtures.
Where most of the debate comes in is with the use of various medications, either for prevention or for treatment.
Pepto-Bismol (or its generic equivalent) has been standard therapy for years. The usual dose is two tablets or two ounces four times a day. It contains salicilate, however, so should not be combined with aspirin or other medications that are affected by aspirin. Common side effects are ringing in the ears, black stools and a black coating on the tongue. Also, it can interfere with the action of certain antibiotics, especially doxycycline which may be required for malaria prophylaxis.
Clay-containing compounds like Kaopectate help to convert liquid stools to formed ones but don't reduce their number or help the associated cramps and nausea. The narcotic-related drugs like Lomotil and Imodium work by slowing bowel function so they do reduce the cramps and nausea. They can also keep the toxins in the intestine, though, so can actually prolong the illness. They should especially not be used in severe cases with blood and mucus in the stools. Also, some countries consider these to be narcotics so their possession has occasionally been known to cause problems with customs.
Yogurt, lactobacillus and activated charcoal, all often recommended, are ineffective.
Since the problem is mostly bacterial, it makes sense that antibiotics would be effective. But they also cause the most problems. The reason that the American Society of Tropical Medicine & Hygiene recommends AGAINST their use is that they produce resistant strains of bacteria. (see Antibiotics) This has become a real problem in Mexico where one antibiotic after another has become ineffective due to its overuse.
The most common antibiotics used these days are Cipro, Floxin or azithromycin, depending on your destination. Sometimes a single dose is effective to stop the diarrhea. These drugs can, however, cause sever sun-sensitivity and lead to sunburn. Doxycycline was in vogue for a while but most people feel that it is now ineffective and besides, it can cause stomach cramps and sunburn. Most of these antibiotics are not recommended for pregnant women.
All of the antibiotics can cause vaginal yeast infections and many women find that to be a worse problem than the diarrhea. Also, any of these medications can cause a disease called pseudomembranous colitis which results in severe, unrelenting diarrhea.
There are some new, oral vaccines against traveler's diarrhea but they are only of limited effectiveness and are so far not available in the United States.
Staying in a given country for a while will eventually provide some immunity but this disappears within a few months after leaving.
So as you can see, there's no perfect answer. What we recommend is to take nothing in advance to prevent the disease but to rely on good hygiene, hand-washing and safe eating habits. If you do get diarrhea, the mainstay is hydration and wait for the illness to wear off. If it is getting severe, then we recommend Imodium and a dose of the appropriate antibiotic to be taken up to twice per day. Usually one dose will suffice. If you start getting severely dehydrated (e.g. stop urinating), run a fever or have blood or mucus in the stools, you need medical attention. And if the symptoms occur or persist for more than a week after returning home you also need to see a doctor as the cause is usually not bacterial.
Certain exceptions need to be made. For instance, people with chronic diseases like diabetes, heart disease, Crohn's disease or AIDS should probably take an antibiotic right from the start. And an important trip where even one day of illness could be disastrous, such as an important business meeting, might also be a good occasion to fortify oneself with medication. In this case, where medication is being taken prophylactically, the best choice may be a new antibiotic called rifaximin.