Traveler’s diarrhea (TD) is a very common health issue for people traveling internationally. It is so common that it is actually the most predictable travel-related illness. Depending on where you are traveling and the time of year, between 30% and 70% of travelers might experience it within a two-week trip. While it was once thought that following strict food rules like “boil it, cook it, peel it, or forget it” could prevent TD, research shows that even careful eaters can get sick. The real culprits are often poor hygiene in local eateries and inadequate public sanitation systems.
TD isn’t caused by one single thing but is a syndrome resulting from various infectious agents that attack the intestines. Bacteria are the most frequent cause, responsible for 80% to 90% of cases. Viruses cause a smaller percentage, about 5% to 15%, though modern testing suggests this might be underestimated. Protozoal infections are less immediate, typically showing up later and accounting for around 10% of diagnoses, especially in travelers on longer trips.
“Food poisoning” is often used to describe illnesses from toxins released by infectious agents (like Clostridium perfringens) or pre-existing toxins in food (like Staphylococcal food poisoning). These toxin-related illnesses can cause both vomiting and diarrhea, but thankfully, symptoms usually clear up on their own in 12 to 24 hours.
Understanding the Infectious Agents Behind Traveler’s Diarrhea
Bacterial Culprits
Bacteria are the primary cause of traveler’s diarrhea. The most commonly identified bacterium is enterotoxigenic Escherichia coli (ETEC). Following ETEC, Campylobacter jejuni, Shigella species, and Salmonella species are also frequent causes. Other types of E. coli, such as enteroaggregative E. coli, are also often found in TD cases. Surveillance studies also indicate that bacteria like Aeromonas, Plesiomonas, and newly identified pathogens such as Acrobacter, enterotoxigenic Bacteroides fragilis, and Larobacter can also lead to TD.
Viral Causes
Viruses are another category of pathogens responsible for traveler’s diarrhea. Common viral culprits include astrovirus, norovirus, and rotavirus.
Protozoal Parasites
Protozoal parasites are less common but significant causes of TD, particularly for longer-term travelers. Giardia is the most frequently identified protozoan. Entamoeba histolytica and Cryptosporidium are less common. Cyclospora risk varies greatly by location and season, with higher risks in areas like Guatemala, Haiti, Nepal, and Peru. Dientamoeba fragilis, a flagellate, is sometimes also linked to diarrhea in travelers.
Who is at Risk of Traveler’s Diarrhea?
Traveler’s diarrhea affects men and women equally. Younger adults tend to be more susceptible than older travelers. Unfortunately, having TD once doesn’t protect you from getting it again on future trips, and it’s even possible to experience multiple episodes during a single journey. Expatriates living in Kathmandu, Nepal, for instance, experienced an average of 3.2 episodes of TD in their first year. Seasonal changes can also influence the risk of diarrhea, with higher rates in South Asia during the hot pre-monsoon months.
Alt text: Image depicting factors increasing traveler’s diarrhea risk, highlighting inadequate sanitation, unsafe food storage due to power outages, and lack of access to safe water and handwashing facilities in certain travel destinations.
Poor sanitation infrastructure significantly increases TD risk. In areas where many people lack proper toilet facilities, environmental contamination with stool is higher, making it easier for disease vectors like flies to spread pathogens. Unreliable electricity can lead to food spoilage due to poor refrigeration, further increasing risk. Lack of safe drinking water is a major factor, contaminating both food and drinks. Inadequate hygiene practices, such as not washing hands properly or using contaminated surfaces and utensils, also contribute significantly. In some regions, handwashing might not be a common practice or easily accessible, meaning handwashing stations might be lacking in food preparation areas.
Effective food handling training programs have been shown to reduce TD risk. However, even in developed countries, improper food handling in restaurants has been linked to TD outbreaks caused by pathogens like Shigella sonnei.
Recognizing the Symptoms of Traveler’s Diarrhea
The time it takes for symptoms to appear after exposure can provide clues about the cause of TD. Toxin-related illnesses typically cause symptoms within just a few hours. Bacterial and viral infections usually have an incubation period of 6 to 72 hours. Protozoal infections generally take longer to manifest, from one to two weeks, and are less likely to cause symptoms in the first few days of travel, except for Cyclospora cayetanensis in high-risk areas.
Bacterial and viral TD usually start suddenly with symptoms ranging from mild cramps and loose stools to severe abdominal pain, bloody diarrhea, fever, and vomiting. Vomiting is more prominent with norovirus infections. Diarrhea caused by protozoa like E. histolytica or Giardia duodenalis tends to develop more gradually with milder symptoms, such as 2 to 5 loose stools per day.
Untreated bacterial diarrhea typically lasts 3 to 7 days, while viral diarrhea usually resolves in 2 to 3 days. Protozoal diarrhea can persist for weeks or even months without treatment. Even after the initial infection clears, TD can sometimes lead to ongoing digestive issues, known as post-infectious irritable bowel syndrome. Other potential long-term effects include reactive arthritis and Guillain-Barré syndrome.
Prevention Strategies for Traveler’s Diarrhea
Currently, there are no vaccines available in the United States for the most common pathogens that cause TD. However, travelers can significantly reduce their risk by adhering to recommended preventive measures. These include being careful about food and beverage choices, using non-antimicrobial prophylactic agents, and practicing thorough hand hygiene with soap and water whenever possible. When soap and water aren’t available, hand sanitizers containing at least 60% alcohol are a convenient alternative for cleaning hands before eating. Vaccines are available for other foodborne and waterborne illnesses like Cholera, Hepatitis A, and Typhoid Fever, which travelers should consider.
Safe Food and Beverage Choices
Being mindful of what you eat and drink is crucial in preventing TD. Detailed guidelines on food and water precautions are available; however, travelers aren’t always able to follow these perfectly. Moreover, factors like restaurant hygiene are beyond a traveler’s control.
Non-Antimicrobial Prophylaxis
Bismuth Subsalicylate (BSS)
Bismuth subsalicylate (BSS), commonly known as Pepto-Bismol, is a well-studied non-antibiotic option for TD prevention. Studies in Mexico have shown that BSS can reduce the incidence of TD by about 50%. Common side effects include blackening of the tongue and stools, and less frequently, constipation, nausea, and tinnitus.
Who Should Avoid BSS?
BSS is not recommended for everyone. People with aspirin allergies, gout, or kidney problems, and those taking anticoagulants, methotrexate, or probenecid should avoid BSS. It’s also not generally recommended for children under a certain age (consult product labeling or a doctor). Those already taking aspirin or salicylates should be cautious as combining BSS can increase the risk of salicylate toxicity. Long-term safety of BSS use beyond 3 weeks hasn’t been established, and due to the frequent dosing and number of tablets needed, it’s not a popular choice for routine TD prophylaxis.
Probiotics
Probiotics like Lactobacillus GG and Saccharomyces boulardii have been investigated for TD prevention in limited studies. However, the results are not conclusive, partly because the quality and consistency of probiotic preparations can vary. Research is ongoing, but currently, there isn’t enough evidence to recommend probiotics for TD prevention.
Bovine colostrum is sometimes anecdotally claimed to be beneficial for TD prevention. However, commercially available bovine colostrum supplements are not FDA-approved, and there’s a lack of robust clinical trial data to support its effectiveness in preventing TD.
Prophylactic Antibiotics: Generally Not Recommended
While older studies showed that antibiotics could reduce diarrhea risk by up to 90%, the risks associated with prophylactic antibiotic use usually outweigh the benefits for most travelers. In rare cases, prophylactic antibiotics might be considered for short-term travelers who are at high risk, such as those with compromised immune systems or significant pre-existing medical conditions.
Fluoroquinolones were once the preferred antibiotics for TD prophylaxis, but increasing antibiotic resistance, particularly in Campylobacter and Shigella, has limited their use. Fluoroquinolones also have potential side effects, including tendinitis, QT interval prolongation concerns, and increased risk of Clostridioides difficile infection. Current guidelines generally advise against their use for prophylaxis. Alternatives like rifaximin and rifamycin SV could be considered in specific situations under medical guidance.
Risks of Antimicrobial Resistance and Other Adverse Effects
Prophylactic antibiotics are generally discouraged for most travelers because they offer no protection against viral or protozoal pathogens and can disrupt the natural balance of gut bacteria, potentially increasing the risk of infections with resistant bacteria. Travelers can become carriers of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE), a risk heightened by antibiotic use abroad.
Using prophylactic antibiotics can also limit treatment options if TD does occur. Travelers relying on prophylaxis would need to carry a different antibiotic to treat severe diarrhea. Additionally, antibiotics can cause allergic reactions and other adverse effects.
Traveler’s Diarrhea Treatment Strategies
Antibiotics for Treatment
The effectiveness of antibiotics for traveler’s diarrhea treatment depends on the specific pathogen and its antibiotic sensitivity. Single-dose antibiotic regimens are generally as effective as multi-dose regimens and can be more convenient for travelers.
Azithromycin
Azithromycin is an alternative to fluoroquinolones for treating TD. However, reduced susceptibility to azithromycin has been observed in some pathogens in certain regions. A common regimen is a single 1,000 mg dose, but this can cause nausea. Taking the dose as two divided doses on the same day can help reduce this side effect.
Fluoroquinolones (Ciprofloxacin, Levofloxacin)
Fluoroquinolones like ciprofloxacin and levofloxacin were traditionally the first-line antibiotics for TD. However, increasing resistance, especially in Campylobacter, particularly in South and Southeast Asia, has made them less reliable in many areas. Resistance is also rising in other pathogens like Salmonella and Shigella. Furthermore, fluoroquinolones carry FDA black box warnings due to potential serious side effects, including aortic tears, hypoglycemia, mental health issues, and tendon problems.
Rifamycins: Rifamycin SV and Rifaximin
Rifamycin SV
Rifamycin SV is a newer FDA-approved option for treating TD caused by non-invasive E. coli in adults. It’s a non-absorbable antibiotic designed to target the lower small bowel and colon. Clinical trials have shown it to be more effective than placebo and comparable to ciprofloxacin for treating TD. However, like rifaximin, it’s effective against non-invasive E. coli, so travelers might need to carry another antibiotic like azithromycin for potential infections caused by invasive pathogens.
Rifaximin
Rifaximin is also approved for treating TD caused by non-invasive E. coli. However, since travelers usually can’t determine if their diarrhea is invasive or non-invasive, and would need to carry a backup antibiotic for invasive cases, its overall practical use as a self-treatment for TD is still being evaluated.
In conclusion, while traveler’s diarrhea is a common travel ailment, understanding its causes, practicing preventative measures, and knowing effective treatment options can help you stay healthy and enjoy your travels. If you experience severe symptoms or symptoms persist, seeking medical advice is always recommended to ensure appropriate and effective traveler’s diarrhea treatment.
