Travellers’ Diarrhoea: What the Evidence Shows
Key takeaways · 16 min read
- A 2025 meta-analysis of 10 cohort studies found that 36% of short-term travellers from high-income countries had diarrhoea; most cases were mild and about 3% severe.
- Destination and trip length matter most: in one Finnish cohort, 80% of travellers to South Asia reported diarrhoea, against 60% of those to Latin America.
- The evidence for “boil it, cook it, peel it” is weak: in one review, 7 of 8 studies found no link between food choices and risk.
- About a third of Dutch travellers came home carrying resistant ESBL-producing gut bacteria, 75% after southern Asia; antibiotics during the trip raised the odds.
Travellers’ diarrhoea is the most common illness of international travel, and one of the least glamorous. It usually means three or more loose stools a day, often with cramps or nausea, starting within the first days of a trip. For most people it costs a day or two; for a few it ends a holiday or leaves a gut that does not settle for months.
The standard advice has hardly changed in decades: drink bottled water, avoid ice and salads, and eat only food that is boiled, cooked or peeled. Studies that have tested that advice are surprisingly unkind to it. Meanwhile, researchers have found a newer, quieter risk: many travellers bring home antibiotic-resistant bacteria in their gut, whether or not they were ill.
This article sets out how common travellers’ diarrhoea is and where, what causes it and how long it lasts, what the research says about food rules, how travel spreads resistant bacteria, and who develops lasting bowel symptoms afterwards. It does not give treatment or medicine advice, which belongs with a doctor or travel clinic.
How common it is
The most recent pooled estimate comes from a 2025 meta-analysis in the Journal of Travel Medicine by Sophie Carroll and colleagues. They combined 10 cohort studies of 8,478 adults from high-income countries on trips of under 100 days, mostly to tropical and subtropical destinations. On average, 36.1% had at least one episode of travellers’ diarrhoea. The studies disagreed widely, and the authors’ prediction interval suggests that a new study could find anything from about 20% to 56%.
One traveller in three, mostly mild
Pooled incidence of travellers’ diarrhoea among short-term adult travellers from high-income countries, by severity, %.
Source: Carroll SC et al., J Travel Med 32(2):taae008 (2025), doi:10.1093/jtm/taae008. 10 cohort studies, 8,478 travellers; severity figures pool four or fewer studies each.
Most of it was mild: 23.6% of travellers had mild diarrhoea, 8.1% moderate and 2.9% severe enough to keep them in bed or send them to a doctor. The numbers also depend on how long researchers keep asking. Studies that followed people for two weeks found 27.7%; those that followed them for four weeks found 49.7%. Studies published in the past decade reported lower rates than older ones, 31.5% against 40.1%, which fits the view that hygiene in many destinations has improved.
The CDC Yellow Book, the US government’s travel-medicine reference, gives a wider range: 30% to 70% of travellers over a two-week period, depending on destination and season. A 2015 review in JAMA by Robert Steffen, David Hill and Herbert DuPont noted that in some parts of the world the risk for a two-week stay has fallen from 20% or more to between 8% and 20%. All of these figures rest on self-reported symptoms.
Where you go matters
Destination is the strongest single factor. The classic three-tier scheme comes from Steffen’s surveys of more than 16,000 charter passengers in the early 1980s. A two-week stay in North America, northern and central Europe, Australia or New Zealand carried a risk of 8% or less. Most of the Caribbean, southern Europe, Israel, Japan and South Africa were intermediate, at 8% to 20%. In lower-income countries the rate ranged from 20% to 55%. Many places have since moved down a tier.
Where Finnish travellers fell ill
Share of 459 Finnish travellers reporting diarrhoea during their trip, by region visited, %.
Source: Lääveri T et al., Clin Microbiol Infect (2018), PubMed 29133155. Volunteers recruited at a travel clinic in Helsinki; self-reported symptoms; small regional groups (40 to 108 people).
Prospective cohorts show how high the risk can still be in some regions. In a Finnish study by Tinja Lääveri and Anu Kantele, 69% of 459 volunteers reported diarrhoea while abroad: 80% of those who went to South Asia, 79% to Southeast Asia and 60% to Latin America. The volunteers came from one travel clinic and the regional groups were small, so the figures are imprecise. Even within one resort area, an outbreak at a single hotel chain, like the one in Cabo Verde, can push local risk far above the regional average.
What causes it
Almost all travellers’ diarrhoea is infectious, picked up from food or water contaminated with faeces. The CDC Yellow Book estimates that bacteria cause 75% to 90% of cases, viruses such as norovirus at least 10% to 25%, and protozoa such as Giardia about 10%, mainly in people who travel for longer. The most common bacterium is enterotoxigenic Escherichia coli, or ETEC, which makes a toxin that draws water into the gut. Campylobacter, Shigella and Salmonella cause many of the more severe episodes.
The mix varies by place. A 2009 systematic review of 51 studies by Nipam Shah and colleagues found ETEC in 30.4% of episodes overall: 33.6% in Latin America and the Caribbean, 31.2% in Africa and 30.6% in South Asia, but only 7.2% in Southeast Asia. Often no cause is found, because the illness resolves before anyone tests a sample.
How long it lasts
Most episodes are short. In Steffen’s 1983 survey of 16,568 returning passengers, diarrhoea lasted 3.6 days on average, with between four and five stools a day. The CDC Yellow Book says untreated bacterial diarrhoea usually lasts three to seven days and viral diarrhoea two to three, while protozoal infections can persist for weeks to months. Symptoms usually begin early: in a cohort of 2,800 European travellers led by Raffaela Pitzurra, the median onset was two days after arrival.
The long tail
Outcomes among 962 European travellers with travellers’ diarrhoea, % of those affected.
Source: Pitzurra R et al., BMC Infectious Diseases 10:231 (2010). 2,800 travellers from Switzerland to resource-limited destinations; self-reported by questionnaire.
The tail matters. In Pitzurra’s cohort, almost two-thirds of those with diarrhoea could carry on with their plans, but one in nine had diarrhoea for more than a week, and 3.8% for two weeks or more. About one in ten was confined to bed or saw a doctor. Steffen’s 2015 review found that 12% to 46% of affected travellers changed their plans. Dehydration is the main short-term danger, and the CDC calls replacing lost fluid the key to treatment.
Boil it, cook it, peel it
The rule is old. Its catchiest form, boil it, cook it, peel it or forget it, has been repeated in travel advice for generations, and the logic is sound: heat kills most pathogens, and peeling removes a contaminated surface. The problem is that when researchers compare travellers who follow food rules with those who do not, the difference is small or absent. In a 1985 study by Markus Kozicki, Steffen and Meinrad Schär of 688 charter passengers to Kenya, West Africa and Sri Lanka, 98% ate or drank traditionally forbidden items within three days.
That study did find that the more dietary mistakes people made, the more often they fell ill. Most later work has been less encouraging. A 2005 review by David Shlim found that 7 of 8 studies that tested the question showed no link between the food people chose and their risk of diarrhoea. Shlim concluded that precautions can work when an expatriate controls their own kitchen, but that poor hygiene in restaurant kitchens is a risk diners cannot see or avoid. The CDC Yellow Book now says that counselling on food and water may not reduce the risk.
Does the rule work?
What studies found when they compared food behaviour with the risk of travellers’ diarrhoea.
| Study | Design | Finding |
|---|---|---|
| Kozicki 1985, 688 passengers | Follow-up after charter flights | 98% broke the rules within 3 days; more mistakes, more illness |
| Shlim 2005 | Review of 8 studies | 7 found no link between food choices and risk |
| Cabada 2006, 5,988 visitors to Cuzco, Peru | Survey at departure | Those given food and water advice were not less likely to be ill |
| Pitzurra 2010, 2,800 Europeans | Prospective cohort | 33.4% of rule-followers still ill; no significant difference |
| Carroll 2025 | Meta-analysis of cohorts | No association with food hygiene practices in 3 studies |
Sources: Kozicki M et al. (1985), PubMed 3988431; Shlim DR, Clin Infect Dis (2005), doi:10.1086/432947; Cabada MM et al., Am J Trop Med Hyg (2006), doi:10.4269/ajtmh.2006.75.968; Pitzurra R et al. (2010); Carroll SC et al. (2025). Food behaviour was self-reported in all studies.
Pitzurra’s cohort tested the rule directly. Of 2,318 travellers who answered the question, 61.6% said they followed it, and 33.4% of them still got diarrhoea; the difference from those who did not follow it was not statistically significant. In Cuzco, travellers who had received food and water advice were, if anything, slightly more likely to be ill. None of this proves the rule is useless. Self-reports of what people ate are unreliable, people who expect to be ill may be the ones who try hardest, and no trial has randomly assigned travellers to follow it.
Precautions may also protect against infections that are rarer but more serious than diarrhoea, such as typhoid and hepatitis A. Guidelines still recommend them, alongside handwashing. What the evidence does not support is the belief that careful eating will keep the risk near zero. In many destinations the main hazard lies in kitchens a traveller never sees, which is why advice increasingly focuses on what to do when diarrhoea starts.
Bringing home resistant bacteria
Some bacteria produce enzymes called extended-spectrum beta-lactamases, or ESBLs, which make them resistant to many common antibiotics. They are far more widespread in the gut of healthy people in parts of Asia and Africa than in northern Europe, and travellers pick them up easily. Carrying them usually causes no symptoms. The concern is that, if a carrier later develops a urinary or blood infection, standard antibiotics may fail, and the bacteria can spread to others at home.
Resistant gut bacteria picked up abroad
Share of travellers who returned colonised with ESBL-producing bacteria, %.
Sources: Arcilla MS et al., Lancet Infect Dis 17(1):78–85 (2017), doi:10.1016/S1473-3099(16)30319-X; Kantele A et al., Clin Infect Dis 60(6):837 (2015), doi:10.1093/cid/ciu957. Different cohorts, years and lab methods.
The largest study is COMBAT, which tested stool samples from 2,001 Dutch travellers before and after their trips. In a 2017 paper in The Lancet Infectious Diseases, Maris Arcilla and colleagues reported that 34.3% of those who left without ESBL-producing bacteria came back with them, and 75.1% of those who went to southern Asia. Taking antibiotics during the trip raised the odds of acquiring them by about 2.7 times, and diarrhoea that persisted after return by about 2.3 times.
A Finnish study of 430 travellers by Kantele and colleagues showed the same gradient: 11% of those with neither diarrhoea nor antibiotics acquired ESBL bacteria, 21% of those with diarrhoea alone and 37% of those with diarrhoea who took antibiotics. For most people the bacteria disappear: in COMBAT the median duration was 30 days. But 11.3% were still colonised a year later, and the estimated chance of passing the bacteria to someone in the same household was 12%.
The bacteria rarely cause illness in the travellers themselves. In a follow-up of 90 Finnish travellers who acquired ESBL bacteria, the main illness linked to them was the diarrhoea itself; three had a urinary infection. The larger worry is at the level of populations, as millions of trips carry resistance genes from high-prevalence regions to low ones. Resistance among the bacteria that cause the diarrhoea itself is also rising: a GeoSentinel study of 859 travellers, published in January 2026, found resistance to fluoroquinolones widespread across regions. Researchers increasingly argue that mild cases, which usually resolve on their own, do not need antibiotics at all.
When it does not stop
For some people the gut does not return to normal after the infection clears. Post-infectious irritable bowel syndrome, or PI-IBS, means recurring abdominal pain with diarrhoea, constipation or both, starting after an episode of gastroenteritis. A 2015 meta-analysis of six studies by Juliane Schwille-Kiuntke and colleagues, as summarised in later reviews, found PI-IBS in 5.4% of people after travellers’ diarrhoea against 1.4% of controls, about three times the risk. Steffen’s 2015 review gave a range of 3% to 17%.
After the trip
New irritable bowel syndrome among Dutch intercontinental travellers, by whether they had travellers’ diarrhoea, %.
Source: Chan J et al., J Travel Med 30(6):taad101 (2023), doi:10.1093/jtm/taad101. COMBAT cohort; Rome III criteria, which the authors say may underestimate the true rate.
The COMBAT cohort gave a prospective estimate. Jiyang Chan and colleagues found that 12.1% of travellers who had diarrhoea developed PI-IBS, against 3.4% of those who did not, and most still had symptoms up to a year later. Cramps, nausea and taking antibiotics during the trip were among the strongest predictors, though antibiotic use may simply mark more severe illness. In GeoSentinel clinic data, more than 40% of travellers seen with gut symptoms lasting over two weeks had PI-IBS rather than an ongoing infection.
Who is most at risk
Beyond destination, the most consistent factors are age and time. In Pitzurra’s cohort, 40.8% of travellers aged 18 to 30 got diarrhoea, against 24.2% of those over 60, and 55.2% of those away for 5.5 to 8 weeks, against 30.3% on trips of up to three weeks. Carroll’s review found that the risk rose with each day of travel and was higher on trips to low-income countries. Younger travellers may eat more adventurously and travel more cheaply, and older travellers may have some immunity from earlier trips.
Style of travel matters too. In one cohort in Carroll’s review, backpackers had about four times the odds of diarrhoea of people on comfortable package trips. Single studies linked higher risk to recent diarrhoea before travel, the use of antacids, which reduce stomach acid, and a travel companion who was ill. People visiting friends and relatives were protected in some studies and not in others. A weakened immune system or chronic bowel disease does not always raise the chance of infection, but it can make an episode more serious.
What the evidence suggests
About one in three short-term travellers to tropical and subtropical regions gets diarrhoea, and the risk depends mainly on destination, trip length and age. Most episodes are mild and last a few days, but about 3% are severe and a minority lead to lasting bowel symptoms. Food rules have weak evidence behind them, mostly because the hazard sits in other people’s kitchens. The newer concern is resistance: a third of travellers return carrying resistant gut bacteria, and taking antibiotics while abroad makes that more likely.
What to do
Steps sorted by when they matter. Each one says how strong the evidence is: Measured Official advice Untested
Before
- Keep the usual food and water precautions and wash your hands. Guidelines still recommend them, partly against rarer infections such as typhoid and hepatitis A. Official advice see Sources
- Plan for what to do if diarrhoea starts. Food rules cannot keep the risk near zero, because the main hazard is in kitchens you never see. Measured see Sources
Afterwards
- If gut symptoms last more than two weeks after a trip, see a doctor. In clinic data, over 40% of such travellers had post-infectious IBS rather than an ongoing infection. Measured see Sources
What not to do
- Do not take antibiotics abroad without need. They make it more likely you bring home resistant gut bacteria. Measured see Sources
Not medical advice. Ask a travel clinic or doctor before you go.
Questions people ask
How likely am I to get travellers’ diarrhoea?
A 2025 meta-analysis put the average at 36% for short trips from high-income countries, with a likely range of about 20% to 56%. It is lower in high-income destinations and higher on long trips to South Asia or Africa.
How long does it usually last?
Usually a few days: bacterial episodes three to seven days and viral ones two to three, according to the CDC. In one cohort, about one in nine lasted more than a week.
Does avoiding salads and ice prevent it?
The evidence is weak. Most studies found little or no difference between travellers who followed food rules and those who did not, though precautions may still help against other infections.
Can I bring back antibiotic-resistant bacteria?
Yes. In a Dutch study, 34% of travellers returned carrying ESBL-producing bacteria, usually without symptoms. Most lost them within a few months, but about one in nine still carried them a year later.
When should I see a doctor?
Guidelines advise medical care for blood in the stool, fever, signs of dehydration, severe illness or symptoms that persist. Gut symptoms lasting weeks after a trip are also worth checking.
The short version
- A 2025 meta-analysis of 10 cohort studies found that 36% of short-term travellers from high-income countries had diarrhoea; most cases were mild and about 3% severe.
- Destination and trip length matter most: in one Finnish cohort, 80% of travellers to South Asia reported diarrhoea, against 60% of those to Latin America.
- The evidence for “boil it, cook it, peel it” is weak: in one review, 7 of 8 studies found no link between food choices and risk.
- About a third of Dutch travellers came home carrying resistant ESBL-producing gut bacteria, 75% after southern Asia; antibiotics during the trip raised the odds.
- In one cohort, 12% of travellers who had diarrhoea developed irritable bowel syndrome afterwards, against 3% of those who did not.
This article summarises published research for general information. It is not medical advice and does not recommend any medicine or dose. Before travelling, talk to a doctor or a travel clinic about your own risks, especially if you are pregnant, travelling with young children or have a long-term illness. If you have diarrhoea with blood, a fever, signs of dehydration or symptoms that do not settle, seek medical care promptly.
Further reading: Carroll et al., Journal of Travel Medicine 32(2) (2025), for the pooled incidence estimates. Arcilla et al., The Lancet Infectious Diseases 17(1) (2017), for the COMBAT study of resistant bacteria. Shlim, Clinical Infectious Diseases (2005), for the evidence on food and hygiene precautions.
- Superbugs: The Race to Stop an Epidemic, Matt McCarthy (2019). A New York doctor’s account of antibiotic resistance and the search for new drugs. Vivid on why resistance matters; it is centred on US hospitals and says little about travel.
- The Gut-Immune Connection, Emeran Mayer (2021). A gastroenterologist on how the gut microbiome, diet and immunity interact. Useful background on the gut; some of its dietary arguments run ahead of the trial evidence.
- An Elegant Defense, Matt Richtel (2019). A journalist explains the immune system through four patients’ stories. Clear and readable on how the body fights infection; it does not deal with travel or diarrhoeal disease.
Sources
Carroll SC, Castellanos ME, Stevenson RA, Henning L. J Travel Med 32(2):taae008 (2025), doi:10.1093/jtm/taae008. — Connor BA, Leung DT. Travelers’ diarrhea. CDC Yellow Book 2026. — Steffen R, Hill DR, DuPont HL. JAMA (2015), doi:10.1001/jama.2014.17006. — Steffen R, van der Linde F, Gyr K, Schär M. JAMA 249:1176–1180 (1983). — Steffen R. Trans R Soc Trop Med Hyg 85(2) (1991). — Lääveri T, Vilkman K, Pakkanen S, Kirveskari J, Kantele A. Clin Microbiol Infect (2018), PubMed 29133155. — Shah N, DuPont HL, Ramsey DJ. Am J Trop Med Hyg (2009), doi:10.4269/ajtmh.2009.80.609. — Pitzurra R, Steffen R, Tschopp A, Mütsch M. BMC Infect Dis 10:231 (2010). — Kozicki M, Steffen R, Schär M. ‘Boil it, cook it, peel it or forget it’: does this rule prevent travellers’ diarrhoea? (1985), PubMed 3988431. — Shlim DR. Clin Infect Dis (2005), doi:10.1086/432947. — Cabada MM et al. Am J Trop Med Hyg (2006), doi:10.4269/ajtmh.2006.75.968. — Arcilla MS, van Hattem JM, Haverkate MR et al. COMBAT study. Lancet Infect Dis 17(1):78–85 (2017), doi:10.1016/S1473-3099(16)30319-X. — Kantele A, Lääveri T, Mero S et al. Clin Infect Dis 60(6):837 (2015), doi:10.1093/cid/ciu957. — Kantele A et al. Clin Infect Dis 70(2):210 (2020). — Boston University School of Public Health news (23 January 2026) on the GeoSentinel study in JAMA Network Open. — Schwille-Kiuntke J, Mazurak N, Enck P. Aliment Pharmacol Ther (2015), doi:10.1111/apt.13199. — Chan J et al. J Travel Med 30(6):taad101 (2023), doi:10.1093/jtm/taad101. — Leder K et al. Ann Intern Med (2013), doi:10.7326/0003-4819-158-6-201303190-00005. — European Centre for Disease Prevention and Control. Epidemiological update on shigellosis and other gastrointestinal infections in travellers returning from Cabo Verde (18 March 2026).
