Traveler's Diarrhea: Causes and symptoms

Bacterial infections are the most common cause of the illness. Viruses and occasional parasites can also be the cause. As for the bacteria involved, toxin producing types of E. coli (called enterotoxigenic) account for approximately 40–60% of cases, with Campylobacter and Shigella each reported in at least 10% of cases. In some studies, Campylobacter has accounted for almost half of the attacks, especially during cooler seasons of the year. The cause can vary depending on several factors, including the season and country visited. More than one organism can be found in 15–30% of cases, and none is identified in up to 40% of cases worldwide.

Rotaviruses and a parvovirus called Norwalk agent are also responsible for TD. Giardia is probably the most common parasite identified, though amoebas (Entamoeba histolytica), Cryptosporidium, and Cyclospora are being found with increasing frequency.

Younger age groups, particularly students, are at greatest risk, probably because of where and what they eat. Individuals over 55 years of age, persons staying with relatives, or business travelers are at lower risk. Foods with the highest chance of transmitting disease are uncooked vegetables, unpeeled fruits, meat, and seafood. Tap water and even ice can be dangerous unless one is sure of the source.

Symptoms usually start within a few days after arrival, but can be delayed for as long as two weeks. Illness lasts an average of three to five days, but is sometimes longer. Cramping abdominal pain, lack of appetite, and diarrhea are the main complaints. In approximately 10% of patients, diarrhea turns bloody and fever develops in about half of those. The presence of bloody bowel movements and fever usually indicates a more severe form of illness and makes Shigella a more likely cause. Medications that decrease the motility or contractions of the intestine, such as loperamide (Imodium) or diphenoxylate (Lomotil), should not be used when fever or bleeding occur.

Diarrhea varies from a few loose stools per day to 10 or more. Dehydration and changes in the normal blood pH (acid-base balance) are the main dangers associated with TD. Signs of dehydration can be hard to notice, but increasing thirst, dry mouth, weakness or lightheadedness (particularly if worsening while standing), or a darkening/decrease in urination are suggestive. Severe dehydration and changes in the body's chemistry can lead to kidney failure and become life-threatening.

Another potential complication is "toxic mega-colon," in which the colon gradually stretches and its wall thins to the point where it can tear. The presence of a hole in the intestine leads to peritonitis and is fatal unless quickly recognized and treated.

Other complications related to TD can involve the nervous system, skin, blood, or kidneys.

— David Kaminstein, MD