• Acute diarrhoeal disease contracted in the industrialised countries is usually caused by a virus, sometimes also Clostridioides difficile in patients who have used antimicrobials.
• Diarrhoea in a traveller (traveller’s diarrhoea) returning from a country with poor hygiene levels is usually caused by bacteria, more rarely a virus or parasite. More than one bacterial pathogen is detected in about one third of travellers.

Aetiology and epidemiology

• Definition: more frequent passage than is normal for the individual of loose or liquid stools within a 24 hour period (WHO)
• The source of contamination is in most cases faecally-contaminated food or drink.
• Risk areas for traveller’s diarrhoea
  • Significant risk: South Asia (60–80%)
  • Medium risk: sub-Saharan Africa, the majority of Central and South America (20–60%)
  • Moderate risk: Caribbean Islands, northern and southern parts of Africa as well as eastern Europe (8–20%)
• Factors that have an influence on the risk of acquiring a gastrointestinal infection include:
  • the characteristics of the microbe (pathogenicity, infective dose etc.)
  • the characteristics of the host (immune defence, including immunity acquired during earlier travels against the same pathogen, genome, acidity of the stomach etc.)
• Bacterial aetiology (50–80%)
  • The three most common findings: EAEC, EPEC, ETEC (see below)
  • Enteroaggregative Escherichia coli (EAEC)
  • Enteropathogenic E. coli (EPEC)
  • Enterotoxigenic E. coli (ETEC)
  • Enterohaemorrhagic E. coli (EHEC)
  • Enteroinvasive E. coli (EIEC)
  • Campylobacter
  • Salmonella
  • Shigella
• Viral aetiology (5–25%)
  • Rotavirus
  • Norovirus
  • Adenovirus
  • Hepatitis A virus
• Parasitic aetiology (< 10%)
  • Giardia duodenalis (Giardiasis)
  • Dientamoeba fragilis (Dientamoebiasis)
  • Cryptosporidium (Cryptosporidiosis)
  • Entamoeba histolytica (Amoebiasis)
  • Cyclospora (Introduction to intestinal protozoal diseases)
• Compare with food poisoning (Food poisoning): starts soon after eating with abdominal pain and vomiting, the clinical picture sometimes also includes diarrhoea; very quick recovery.
  • Causative agents
    • Staphylococcus aureus
    • Clostridium perfringens
    • Bacillus cereus

• Usually starts during the first week of travel.
• The average duration is 3–5 days; in 2–3% of cases disease duration exceeds 2 weeks, in 1–2% duration exceeds one month.
• Traveller’s diarrhoea is in more than 90% of cases a mild to moderate and self-limiting disease; less than 1% of cases require hospitalisation.
• Symptoms
  • Abdominal pain in 35–75%
  • Nausea in 15–50%
  • Fever in 30%
  • Muscle pains in 25%
  • Invasive bacteria cause a disease that is often more severe than that caused by non-invasive bacteria (cf. salmonella septicaemia)
  • Protozoans are only rarely the cause of acute diarrhoea
    • Cryptosporidium may cause profuse watery diarrhoea that lasts even for several weeks.
    • Amoebiasis is often characterised by bloody diarrhoea, and the symptoms may be severe.
  • Severe disease may result in dehydration and acidosis.
• Possible complications
  • Reactive arthritis (salmonella, shigella and campylobacter infections) (Reactive arthritis)
  • Guillain–Barré syndrome (campylobacter infection) (Guillain-Barré syndrome (polyradiculitis))
  • Haemolytic-uraemic syndrome (EHEC infection)

• The disease usually resolves spontaneously and no bacteriological diagnosis is needed. A stool specimen does not therefore need to be obtained from all patients.
• The routine investigation is nucleic acid detection testing.
  • A combination of gene-amplification based nucleic acid detection test and stool culture of faecal pathogens detects the pathogen in almost 80% of cases.
  • Specimens positive for salmonella, shigella, yersinia, campylobacter or EHEC in the nucleic acid detection test are further investigated with culture and, if needed, with sensitivity testing without a separate order.
  • The method that is based on nucleic acid detection is not able to distinguish between EIEC and Shigella. Diagnosis of Shigella requires positive culture results.
  • The results of the sensitive nucleic acid detection test should be interpreted in relation to the clinical picture. The method is not used to investigate asymptomatic persons.
• Other investigations in an acute disease as per symptom picture
  • Nucleic acid detection test for Clostridium difficile in patients who have taken antimicrobials. This sensitive test is not needed in persons with no symptoms. In children below 2 years of age, C. difficile is a part of normal intestinal flora.
  • In severe watery diarrhoea, a Vibrio cholerae culture may be indicated.
  • In acute amoebic colitis, stained stool sample for the detection of amoebas
  • In prolonged watery diarrhoea with an abrupt onset, the stools should also be examined for Cryptosporidium. It can be identified either by nucleic acid detection test for intestinal parasites or by staining. Cryptosporidium staining will also isolate Cyclospora.
  • The isolation of parasites is usually only indicated if diarrhoea persists (for example, Giardia or Dientamoeba). See Prolonged abdominal complaints in travellers for more details (Prolonged abdominal complaints in travellers)).
• Serological methods (salmonella, campylobacter and yersinia antibodies) are not useful in the aetiological evaluation at the early stages of the disease.
• Acute diarrhoea in those employed in risk occupations as defined by national legislation is investigated with stool cultures. See also (Food poisoning).
  • See national and local guidelines as to the type of notification that is required for the different diseases.

• Basic treatment: rest and fluids
• Fluid replacement
  • In addition to the body’s basic needs, fluids lost due to symptoms (diarrhoea, vomiting, fever, sweating) must be replaced, several litres a day in a hot climate.
  • Tea, bottled water, diluted juice, milk and if necessary Oral Rehydration Solution (ORS) which is indicated for prevention and treatment of dehydration, as well as for restoration of sodium balance.
  • Preparation of ORS liquid at home:
    • 1 level teaspoon of salt
    • 8 level teaspoons of sugar
    • dissolved and mixed in 1 litre of clean water.
  • ORS powder packets are available in pharmacies in tropical regions. The contents are dissolved in 1 litre of bottled water.
  • Of particular importance in young children and the elderly, in whom the disease may easily lead to dehydration
• Symptomatic medication
  • Loperamide
    • For no longer than a few days
    • Not for children under 12 years
    • Adult dose: initially 4 mg, and then 2 mg after each episode of diarrhoea; maximum daily dose is 12–16 mg
    • Should be started cautiously as may cause constipation even after a total dose of 6 mg.
    • Not for a patient with fever or bloody diarrhoea (possibility of invasive bacteria), may be harmful.
  • There is no evidence on the efficacy of probiotics in the treatment of traveller’s diarrhoea.
  • No charcoal tablets as they may, among other things, prevent the absorption of other medicines.
  • Antimicrobials
    • Not for routine use
    • Indicated in the following cases: high fever, obvious bloody diarrhoea (except in EHEC infection), the patient is unwell, severe clinical picture
    • Indicated if diarrhoea can be expected to worsen a pre-existing underlying disease (inflammatory bowel diseases, immunodeficiency, cardiac insufficiency, history of reactive arthritis etc.).
    • If possible, the results of stool investigations should be awaited.
    • Shigellosis must always be treated in symptomatic persons since the infective dose is small, and it is easily transmissible. This rule applies only in Shigella infection that has been confirmed by culture. Infection detected by nucleic acid detection (EIEC/Shigella) must be verified by culture.
    • Disease caused by Shigella usually resolves spontaneously and when the results of the culture become available the patient may already be asymptomatic. Asymptomatic patients need no treatment with antimicrobials, unless it is relevant for prophylactic measures in risk groups (e.g. children in daycare or food workers). Since Shigella causes a dangerous communicable disease, consulting a physician locally responsible for communicable diseases may be warranted, especially regarding treatment of risk groups. Find out about local policy and responsibilities.
    • Campylobacter infection requiring pharmacotherapy is treated with azithromycin.
    • Empiric treatment if antimicrobial drug therapy is considered necessary
      • Usually ciprofloxacin 500 mg twice daily, treatment period 1–3 days (if an underlying disease is the indication for therapy, treatment period should be longer) or azithromycin 500 mg once daily for 1–3 days.
      • Where the disease was contracted in Southeast Asia, the treatment is azithromycin 500 mg once daily for 1–3 days (campylobacter is common, resistance to ciprofloxacin is common).
      • Pregnant women should be given ceftriaxone or a macrolide.
      • An infection that requires hospitalisation is treated with ceftriaxone.
  • General principles for the use of antimicrobials
    • Antimicrobials should generally be avoided in the treatment of mild and moderate disease – they may do more harm than good. For shigellosis verified by culture, see above.
    • Adverse effects: antibiotic diarrhoea; an increased risk of colonisation, infections or prolonged carrier status by resistant intestinal microbes; the impact of a course of antimicrobials on the balance of intestinal microbial flora (detectable even for several years); risk of diarrhoea caused by Clostridioides difficile overgrowth etc.

• Follow-up is necessary if the patient’s occupation is associated with a higher than normal risk of disease spread or the occupation is such that the consequences of an infection would be more serious than usual.
  • Local legislation may define specific groups that require follow-up.
  • Such requirements may apply, for example, to persons that handle foodstuffs or who are involved in production of unpasteurized dairy products.
• An employee in any of the above groups who develops gastroenteritis/diarrhoea must not return to his/her duties (regardless of the causative agent).
  • If a stool culture has isolated EHEC, salmonella or shigella, the employee must be kept away from work until a negative sample is obtained.
  • If no EHEC, salmonella or shigella is isolated, the employee may return to work after 2 days with no symptoms.
  • In campylobacteriosis, the employee may return to work as soon as the symptoms subside.
• Follow-up specimens are only necessary for individuals in risk groups (possibly defined in local legislation), others are considered cured of diarrhoea at the end of symptoms.
• A doctor or a dentist must report the following communicable diseases to the authorities in most countries:
  • Cholera
  • Enterohaemorrhagic E.coli (EHEC) enteritis
  • Shigellosis
  • Systemic diseases that may be associated with diarrhoea
    • Hepatitis A
    • Hepatitis E
    • Paratyphoid
    • Typhoid
  • As an exception to this general principle, diseases caused by rotavirus and salmonella, other than typhoid and paratyphoid, are usually only reported by the laboratory. Local differences may exist. Find out about local practices.
• See also article Food poisoning (Food poisoning).

• The risk of contracting traveller’s diarrhoea is more dependent on the level of hygiene in the travel destination than on the behaviour of the traveller.
• Good hand and food hygiene should be aimed at in all settings.
• Hands are washed with soap or a disinfectant is used before touching food and eating and always after a visit to the lavatory [Evidence Level: A].
• Anyone with diarrhoea should not handle shared foodstuffs.
• Safe foodstuffs
  • Bread and other grain products
  • Fresh fruit peeled by the person himself/herself
  • Freshly prepared fish and meat dishes and soups, cooked thoroughly and served hot
  • Boiled or otherwise cooked vegetables, served hot
  • Bottled drinks and water, preferable carbonated
• Disinfection of water that is not bottled (boiling and filtering)
• Foodstuffs to be avoided
  • Street food
  • Salads based on mayonnaise and foods containing egg
  • Insufficiently cooked meat, fish or other seafood, served cold or lukewarm
  • Cold meats
  • Fruit and vegetables that cannot be washed or peeled
  • Cold desserts
  • Unpackaged milk, cream, ice cream, butter, cream cheese
  • Tap water and ice cubes in soft drinks
• Antimicrobials
  • Prophylactic antimicrobials are not recommended.
  • Travellers in special groups only may be given a course of antimicrobials to be used in case symptoms develop (for example, significant immunosuppression, severe cardiac insufficiency, history of reactive arthritis (Reactive arthritis)).
• Probiotics
  • Their prophylactic effect is very low (8%) and they are not routinely recommended.

• No vaccine exists against common traveller’s diarrhoea.
• Oral cholera vaccine
  • Protects against cholera, which only rarely is the cause of common traveller’s diarrhoea [Evidence Level: B].
  • Cholera vaccine is recommended for those travelling to poor hygiene conditions in regions where cholera is endemic or epidemic (cf. refugee camps).
  • Will also give protection against some ETEC strains through a cross reaction; however, prophylaxis against common traveller’s diarrhoea is not an official indication for the vaccine.
• Oral typhoid vaccine [Evidence Level: A]
  • According to immunological studies may offer, in addition to typhoid, partial protection against paratyphoid and the most common salmonella-induced diarrhoeal diseases; prophylaxis against common traveller’s diarrhoea is not an official indication for the vaccine.