Traveler’s diarrhea may be caused by any of several bacteria, viruses, or, less commonly, parasites.
The most common cause of traveler's diarrhea is
E. coli is common in the water supplies of areas that lack adequate purification. Infection is common among people traveling to developing countries.
Norovirus infection has been a particular problem on some cruise ships.
Both food and water can be the source of infection. Travelers who avoid drinking local water may still become infected by brushing their teeth with an improperly rinsed toothbrush, drinking bottled drinks with ice made from local water, or eating food that is improperly handled or washed with local water. People taking drugs that decrease stomach acid (antacids, H2 blockers, and proton pump inhibitors) are at risk of more severe illness.
Nausea, vomiting, hyperactive bowel sounds, abdominal cramps, and diarrhea begin 12 to 72 hours after ingesting contaminated food or water. Severity is variable. Some people develop fever and myalgias. Most cases are mild and self-limited, although dehydration can occur, especially in warm climates.
The mainstay of treatment of traveler's diarrhea is fluid replacement and an antimotility drug such as loperamide. For adults and children ≥ 12 years, loperamide dosing is 4 mg orally initially, followed by 2 mg orally for each subsequent episode of diarrhea (maximum of 6 doses/day or 16 mg/day). An alternative for adults is diphenoxylate 2.5 to 5 mg orally 3 times a day or 4 times a day in tablet or liquid form. The dose of loperamide for children 13 to 21 kg is 1 mg after the first loose stool then 1 mg after each subsequent loose stool (maximum dose is 3 mg/day); for children 21 to 28 kg, 2 mg after the first loose stool then 1 mg after each subsequent loose stool (maximum dose is 4 mg/day); and for children 27 to 43 kg, up to age 12, 2 mg after the first loose stool followed by 1 mg after each subsequent loose stool (maximum dose is 6 mg/day). Antimotility drugs are contraindicated in patients with fever or bloody stools and in children < 2 years. Iodochlorhydroxyquin, which may be available in some developing countries, should not be used because it may cause neurologic damage.
Generally, antibiotics are not necessary for mild diarrhea. In patients with moderate to severe diarrhea (≥ 3 loose stools over 8 hours), antibiotics are given, especially if vomiting, abdominal cramps, fever, or bloody stools are present. For adults, recommended oral antibiotics include ciprofloxacin 500 mg 2 times a day for 3 days or levofloxacin 500 mg once a day for 3 days, although fluoroquinolone resistance appears to be increasing in some areas, particularly in Campylobacter. Alternatives include azithromycin 500 mg once a day for 3 days or rifaximin 200 mg 3 times a day for 3 days. For children, azithromycin 5 to 10 mg/kg once a day for 3 days is preferred.
Travelers should dine at restaurants with a reputation for safety and avoid foods and beverages from street vendors. They should consume only cooked foods that are still steaming hot, fruit that can be peeled, and carbonated beverages without ice served in sealed bottles (bottles of noncarbonated beverages can contain tap water added by unscrupulous vendors); uncooked vegetables (particularly including salsa left out on the table) should be avoided. Buffets and fast food restaurants pose an increased risk.
Prophylactic antibiotics are effective in preventing diarrhea, but because of concerns about adverse effects and development of resistance, they should probably be reserved for immunocompromised patients.