Travellers' Diarrhea

Travellers' diarrhea (TD) is the sudden onset of abnormally loose or frequent stools occurring during or shortly after international travel, most often within the first 2 weeks at a destination given its short incubation period.^[1] It is one of the most common travel-related health problems and one of the most frequent travel-health consultations a community pharmacist provides — both before departure, where destination-risk-stratified counselling and self-treatment-kit preparation are core pharmacist tasks, and at the point of need, where the traveller is often self-managing without reliable access to medical care. Most TD is bacterial, predominantly enterotoxigenic and enteroaggregative Escherichia coli, with Campylobacter, Salmonella and Shigella also common; norovirus, astrovirus and rotavirus cause most viral TD, and Giardia and Cryptosporidium are the leading protozoal causes.^[1] TD is generally self-limited, but its clinical course cannot be reliably predicted at onset, and an episode does not protect against a second episode on the same trip. This chapter covers the traveller-specific angle of acute diarrhea — destination risk stratification, prevention counselling, and severity-matched self-treatment; general acute-diarrhea principles (non-traveller etiology, testing thresholds, Clostridioides difficile) are covered separately in Acute Diarrhea in Adults and become relevant again once a traveller has returned home.

Typical presentation

Abrupt onset of loose or watery stools, typically within the first 2 weeks at a higher-risk destination, often with abdominal cramping, urgency, nausea and malaise. Severity is classified by functional impact on the traveller's planned activities, not by stool frequency, since this is what actually drives the self-treatment decision.^[1]

Causative pathogens

Knowing the dominant pathogen categories explains why empiric antibiotic choice differs by destination and by presentation.^[1]

• Travel to an intermediate- or high-risk destination — most of Asia, the Middle East, Africa and Latin America are high-risk (attack rate over 20% in the first 2 weeks); parts of Southern/Eastern Europe, Israel, South Africa, and some Caribbean and Pacific islands are intermediate-risk (8% to 20%); Western Europe, the United States, Canada, Australia, New Zealand and Japan are low-risk (under 8%).^[1][2]
• Travel during the hot or rainy season, which raises TD attack rates at many destinations, particularly in South Asia.
• Itinerary and accommodation type — backpacking, rural travel, and travel with less-controlled food preparation carry higher risk than resort- or cruise-based travel with more reliable food-safety standards.
• Reduced gastric acidity — proton pump inhibitor or H2-receptor antagonist use increases susceptibility to enteric infection; reassess the ongoing need for these agents before travel to a high-risk destination.
• Prior gastric surgery or another cause of achlorhydria.
• Underlying gastrointestinal disease — inflammatory bowel disease or a history of irritable bowel syndrome.
• Immunocompromise or significant comorbidity — heart failure, insulin-dependent diabetes, inflammatory bowel disease and chronic kidney disease all raise the risk of TD complications and are specifically relevant to pre-travel prophylaxis and vaccine decisions.
• Food and beverage choices at the destination — raw or undercooked food, unpasteurized dairy, tap water or ice, and food from street vendors.
• Local sanitation and food-handling infrastructure at the destination — a larger overall driver of risk than an individual traveller's own precautions.

History

• Exact itinerary — destinations visited, urban versus rural, and dates — since this determines the applicable risk tier and the most likely resistant pathogens for empiric antibiotic selection.
• Timing of onset relative to travel — TD typically begins within the first 2 weeks at a destination; new diarrhea starting well into a long trip, or well after return, needs the general acute/persistent diarrhea approach rather than assumptions specific to arrival-related TD.
• Whether a pre-travel self-treatment kit (loperamide, bismuth subsalicylate and/or an antibiotic) was prescribed, and whether it has already been used, and at what dose.
• Functional severity — whether symptoms are tolerable, distressing, or incapacitating — this is what actually drives the treatment decision, not stool count.
• Presence of blood or mucus in the stool, and fever.
• Hydration status — thirst, urine output, dizziness, ability to tolerate oral fluids.
• Vaccination status (Dukoral) and any antibiotic prophylaxis taken.
• Comorbidities and immunosuppression, and current medications (including proton pump inhibitors/H2-receptor antagonists and anticoagulants, both relevant to treatment choice).
• For a returning traveller: exact date of return, and whether diarrhea has persisted 2 weeks or more.

When to test, and when not to

Persistent post-travel diarrhea — what else to consider

Diarrhea persisting after return is frequently post-infectious irritable bowel syndrome, which is common following TD. Also consider a specific parasitic infection, antibiotic-associated colitis (particularly if an antibiotic was used for TD itself), disaccharidase (lactose) deficiency, and bowel malignancy in an older traveller with a new bowel-habit change. An episode of TD can also unmask previously undiagnosed inflammatory bowel disease or celiac disease.^[1]

• Reduce the risk of acquiring TD through pre-travel counselling and destination-appropriate prevention measures.
• Maintain hydration throughout the illness, regardless of severity or cause.
• Limit the duration and severity of symptoms, minimizing disruption to the itinerary.
• Match treatment intensity to functional severity — avoid unnecessary antibiotic exposure in mild disease, and avoid under-treating severe or dysenteric disease.
• Avoid worsening an invasive/dysenteric infection through inappropriate antimotility-agent use.
• Recognize when self-treatment has failed and medical care is needed, whether abroad or after return.
• Minimize the traveller's contribution to antimicrobial resistance and multidrug-resistant organism (MDRO) acquisition/transmission.

Food and water precautions

"Boil it, cook it, peel it, or forget it" is a useful mnemonic, but counsel honestly: following these precautions reduces but does not eliminate risk — a traveller who follows the rules carefully can still become unwell, since local restaurant hygiene and destination sanitation infrastructure are the larger drivers of risk. Still worth practicing consistently:

• Drink only boiled, bottled (cap sealed and intact) or carbonated beverages; alcohol does not sterilize water or ice.
• Use ice only if made from safe water.
• Eat fruit (including tomatoes) only if washed in safe water and peeled; avoid salads and raw vegetables.
• Eat only thoroughly and recently cooked meat and fish; avoid leftovers and condiments left in open containers.
• Avoid food from street vendors.
• Wash hands with soap and water before eating; an alcohol-based hand sanitizer is an effective substitute when hands are not visibly dirty.

Water disinfection, when a safe supply is not otherwise available

• Heat — organisms are killed within seconds at boiling temperature, but boil for 1 minute to be safe.
• Filtration — effectiveness depends on filter pore size; follow filtration with chemical disinfection when possible.
• Chemical disinfection — chlorine (sodium hypochlorite or chlorine dioxide) or iodine (2% tincture, 5 drops per litre of clear water) as tablets or liquid. Limit iodine to a few weeks of emergency use given its physiologic effects, and use iodine resin filters (which transfer iodine to the organisms rather than leaving it in the water) where iodine exposure needs to be minimized.
• Ultraviolet (UV) light — kills bacteria, viruses and other parasites, but does not work in cloudy water; portable battery-operated units are available.

Reassess acid-suppressing therapy before high-risk travel

Reassess the ongoing need for a proton pump inhibitor or H2-receptor antagonist before travel to a destination with a high TD rate, since reduced gastric acidity increases the risk of acquiring an enteric pathogen.

Diet during an active episode

A simple diet that maintains hydration, contains a modest amount of sugar and electrolytes, and avoids fatty/oily foods and natural laxatives (caffeine, alcohol, excess fruit) is best tolerated. Bananas help replace mild potassium losses; dietary fibre can aggravate bloating and cramping during active symptoms.

Pregnancy

Pregnant travellers may be at increased risk of TD and its complications, since significant volume depletion can precipitate premature labour, placental insufficiency or shock — early fluid, energy and electrolyte replacement is the cornerstone of management.^[1]

Avoid chemoprophylaxis in pregnancy — it is not recommended regardless of destination risk.

Loperamide is considered safe and can be used when needed.

Azithromycin is considered safe in pregnancy and is the antibiotic of choice if treatment is needed.

Avoid bismuth subsalicylate (bismuth encephalopathy risk) and fluoroquinolones (contraindicated in pregnancy, though the short courses used for TD have not been shown to increase teratogenicity).

Iodine is not recommended as a water disinfectant in pregnancy given a potential risk of fetal thyroid disease — recommend boiling, filtration or chlorine-based disinfection instead.

Breastfeeding

Continue breastfeeding during travel — it reduces the infant's own risk of acquiring a food/water-borne infection. Meticulous handwashing and breast hygiene limit transmission of infecting organisms to the infant.

Azithromycin and loperamide may be used for TD during breastfeeding. Avoid iodine water disinfection, bismuth subsalicylate and fluoroquinolones while breastfeeding.

Pediatrics

Children are at increased risk of rapid, severe dehydration — start oral rehydration therapy early and travel with a commercial oral rehydration product. Rotavirus is a more prominent cause in children under 3 than in adults.

Do not use loperamide in children under 2 years, or in a child who is malnourished, moderately-to-severely dehydrated, systemically unwell, febrile, or has bloody diarrhea — adverse effects outweigh benefit in these situations.

Loperamide may be used with caution in travelling children over 2 years old, limited to 2 days of treatment; see Drug Tables for weight-based pediatric dosing.

Bismuth subsalicylate is contraindicated in children under 2 years, and should be used cautiously in older children given the Reye syndrome risk associated with its salicylate component.

Azithromycin is the paediatric antibiotic of choice for TD when treatment is needed. Ciprofloxacin has traditionally been avoided in children over concern for cartilage effects, but the short 1-3 day courses used for TD are considered acceptable when specifically indicated. Trimethoprim/sulfamethoxazole is limited by the same resistance seen in adults.

Older adults

Dehydration develops faster and can present atypically (confusion, falls) rather than with classic thirst — have a lower threshold to start oral rehydration therapy and to seek medical care if oral intake cannot keep pace with losses, particularly for a frail traveller with limited reserve.

Immunocompromised travellers and those with significant comorbidity

These travellers carry a higher risk of TD complications and are the group for whom pre-exposure antibiotic prophylaxis is most often genuinely appropriate (see Choose Initial Treatment). Have a lower threshold to seek medical care rather than continuing self-treatment if symptoms are more than mild.

Renal impairment

Use bismuth subsalicylate with caution given reduced clearance of the salicylate component. Confirm current renal dose adjustment for rifaximin and for any fluoroquinolone before recommending in significant renal impairment.

During travel, reassess functional severity and hydration status regularly — ask about the number and character of stools, ability to tolerate oral fluids, and whether planned activities are still possible. Escalate to medical care rather than continuing self-treatment if symptoms have not improved within 48 hours of an appropriately severity-matched regimen, or if new red-flag features develop (blood, high fever, signs of dehydration).^[1] After return, investigate diarrhea that has persisted 2 weeks or more with stool culture and ova/parasite testing as first-line tests, since post-infectious irritable bowel syndrome, a specific parasitic infection, and (if an antibiotic was used) antibiotic-associated colitis are all more likely the longer symptoms persist. On the next visit, confirm the traveller's self-treatment kit was actually used correctly (right agent, right severity trigger), and counsel that a traveller treated with antibiotics abroad may carry a multidrug-resistant organism for a period after return — this is relevant context for any future prescriber, particularly around subsequent infections or hospitalization.^[3]

1. Confirm correct use of oral rehydration therapy and of loperamide/bismuth subsalicylate at labelled doses, and re-screen for any red-flag feature that may not have been present at onset.
2. If mild self-treatment (loperamide and/or bismuth subsalicylate alone) has not controlled symptoms, or severity has escalated to moderate/severe, add or switch to a destination-appropriate antibiotic per the severity/destination rule.
3. If a single-dose antibiotic has not improved symptoms within 24 hours, extend to the full 3-day course of the same agent before assuming treatment failure.
4. If symptoms genuinely fail a full antibiotic course, or dysentery/high fever/dehydration is present at any point, seek local medical care rather than repeating or escalating self-treatment further — this may reflect a resistant pathogen or an invasive infection needing specific management.
5. After return home, if diarrhea persists 2 weeks or more despite appropriate treatment, pursue the persistent-diarrhea workup (stool culture, ova and parasite testing) rather than continuing empiric antidiarrheal self-treatment.
6. If the infectious workup is negative and symptoms persist, reassess for a non-infectious cause — post-infectious irritable bowel syndrome, unmasked inflammatory bowel disease or celiac disease, or lactose intolerance.

• Using loperamide as monotherapy — or at all without real caution — in bloody diarrhea/dysentery or in TD with high fever.
• Defaulting to a fluoroquinolone as first-line empiric therapy for a South or Southeast Asian itinerary despite well-documented Campylobacter fluoroquinolone resistance there.
• Prescribing routine antibiotic prophylaxis for an average traveller — this is reserved for narrow, specific high-risk situations, not standard pre-travel counselling.
• Recommending bismuth subsalicylate to a traveller on an anticoagulant or another salicylate, or to a pregnant traveller or a child under 12.
• Giving food/water precaution counselling as though it were fully protective, rather than honestly framing it as a real-but-incomplete risk reduction.
• Sending a traveller to an intermediate- or high-risk destination without a self-treatment kit (loperamide, bismuth subsalicylate and an itinerary-appropriate antibiotic) when one is clinically appropriate.
• Recommending iodine-based water disinfection for a pregnant traveller.
• Continuing self-treatment well beyond 48 hours without improvement instead of directing the traveller to seek medical care.
• Missing malaria as a cause of fever in a traveller who also has diarrhea and a malaria-endemic itinerary.
• Treating persistent post-travel diarrhea (2 weeks or more) with continued antimotility/antibiotic self-treatment instead of pursuing stool studies.
• Failing to warn against nonprescription antidiarrheal products purchased abroad, some of which contain chloramphenicol or iodochlorhydroxyquin.
• Reflexively using antibiotics for every case of moderate TD rather than reserving them for when loperamide/bismuth subsalicylate alone is failing or symptoms are more than mild — unnecessary antibiotic use increases MDRO acquisition risk without benefit in truly mild disease.^[3]

How to use this table: Doses are adult doses unless otherwise labelled and require patient-specific confirmation, including renal adjustment. Levofloxacin is linked below to its oral/IV Drug Database monograph, not the inhaled Quinsair monograph that shares the bare "levofloxacin" name in this database — the inhaled formulation is not relevant to travellers' diarrhea. Select any drug name to open its complete Pharmasist Drug Database page.

Oral Rehydration Therapy

Intestinal Adsorbents

Antimotility Agents

Fluoroquinolones

Resistance has increased and geographic patterns have evolved — avoid as the empiric first choice for South/Southeast Asia and the Indian subcontinent, where fluoroquinolone-resistant Campylobacter and Shigella are common.^[1]

Macrolides

Semi-synthetic Rifamycin Antibiotics

Vaccines