Travelers’ Diarrhea

Acute diarrhea associated with travel is referred to as travelers’ diarrhea (TD) and is the most frequent illness among travelers. TD is defined as an acute illness associated with an increase in frequency and change in stool form (loose or liquid) compared with normal in an individual from one region who has traveled to another. It is frequently associated with other gastrointestinal symptoms that may include nausea, distention, urgency, and abdominal cramps as well as systemic symptoms such as fever, muscle aches, joint aches, and malaise. On average untreated bacterial diarrhea lasts 3 to 7 days. When accompanied by bloody stools and high fever, it is often termed dysentery. Persistent (2 to 4 weeks) or chronic (>30 days) diarrhea can also manifest, but it is a less frequent occurrence.

Although TD occurs more frequently in travelers visiting resource-poor settings, it can also occur among travelers worldwide. Higher risk regions include Central America and northern South America, Africa, the Middle East, and Asia (not including Japan); some Caribbean islands, China, and eastern European countries are intermediate-risk destinations; and North America, northern and western Europe, Australia, New Zealand, Japan, and a number of other Caribbean islands are low-risk destinations. Average attack rates for a 2-week itinerary are estimated to be 10% to 40%, although higher rates can occur based on location and itinerary and season of travel.

Risk factors for developing TD beyond location include age, itinerary type, duration of travel, source of meals, comorbidities, and medication. Younger travelers are generally at higher risk, and travel itineraries where food and water are consumed frequently from unhygienic sources pose greater risk. There is a greater incidence of TD in younger, more adventurous travelers. Bacteria are the predominant cause of acute TD and viruses (mainly norovirus) can account for 10% to 15%. Onset is usually during travel, as common infectious causes have relatively short incubation periods; however, illness frequently occurs on the transit home or shortly after return as well. Parasites are relatively rare and usually occur with more austere itineraries, in adventurous travels, and on longer trips; symptoms may not appear until well after a traveler returns home, and they can be prolonged.

Due to ubiquitous exposure and low inoculation doses for some pathogens, prevention of TD is a challenge. TD is best managed by the traveler through pretravel counseling, with a heavy emphasis on appropriate hydration/rehydration, provision of antibiotics and loperamide to take when ill, and recommendations on appropriate follow-up and testing in case of self-treatment failure, prolonged illness, or severe symptoms.

A 21-year-old man traveled to a resort in Mexico for his spring break holiday. He had traveled to Mexico before, and each time he was there he developed diarrhea. This time, he asked his doctor what he could do to avoid getting sick. His doctor reviewed food and water precautions, telling him to eat only freshly cooked foods served hot, to avoid the local water and anything washed in water, and to avoid eating food prepared by street vendors. During his trip he decided to take a probiotic on a daily basis, beginning a day before his trip and continuing for the duration. He was fine during the week he was in Mexico, carefully avoiding salads at the buffet and drinking only carbonated bottled beverages, including beer. On the plane ride home, he developed a sudden onset of cramps and diarrhea. He continued to have symptoms after arriving at home. He then returned to see his doctor and reported that he had been very careful about his diet. He took his probiotics faithfully but may have had ice in a margarita 2 days before he got sick.

The patient’s physical examination was unremarkable, and there was no blood or mucus in the stool. The doctor suggested a single dose of azithromycin 1000 mg, which the patient took. By the end of the day, he felt better. He continued to have loose stool for some 24 hours, after which his symptoms resolved completely.

COMMENT: This vignette highlights a few important points. Younger individuals are more likely to get sick with travelers’ diarrhea. Whether this is related to more adventurous food consumption, a lack of acquired immunity, or other factors is unclear. Despite the patient’s attention to food and water precautions, it is very difficult on a vacation to adhere to these recommendations fully. It is possible that the ice cubes in his margarita were responsible for his illness, although often the source of contamination is unknown. In addition, even with the most careful food and water precautions, one can never completely eliminate the risk of travelers’ diarrhea at an at-risk destination. Many factors are beyond the traveler’s control. Information regarding the symptoms of travelers’ diarrhea and possible mitigation strategies (e.g., attention to hydration, self-treatment either with nonantibiotic remedies such as loperamide or bismuth subsalicylate or even a single dose or short course of an appropriate antibiotic) can be usefully offered to individuals planning to travel. The patient’s clinical presentation is most consistent with a bacterial diarrhea with a fairly sudden onset of uncomfortable diarrhea. Diarrhea in the first week of travel is almost always bacterial, although viral pathogens may present with a fairly short incubation period; however, they are generally associated with vomiting. Most enteric parasitic pathogens have an incubation period of at least 7 to 10 days.