Diarrhea, Acute



  • An abnormal increase in stool water content, volume, or frequency (≥3 stools above baseline in 24 hours) for <14 days duration
  • Most commonly secondary to infectious etiology; often self-limited
  • Acute viral diarrhea (50–70%)
    • Most common cause of infectious diarrhea; noninflammatory (watery)
    • Frequently presents with associated nausea and/or vomiting
    • Symptoms usually develop after an incubation period of ~1 day and last for 1 to 3 days; typically self-limited
  • Bacterial diarrhea (15–20%)
    • Most common infectious cause of inflammatory (bloody) diarrhea
    • Incubation period variable; diarrhea is caused by preformed enterotoxin presents within 1 to 6 hours of contaminated food ingestion, whereas bacterial infection typically presents within 1 to 3 days.
    • Symptoms usually resolve in 1 to 7 days; antibiotic use attenuates length and/or severity of disease.
    • Suspect when concurrent illness in others who have shared potentially contaminated food.
  • Protozoal infections (10–15%)
    • Typically cause noninflammatory (watery) diarrhea
    • Long incubation period and prolonged disease course; symptoms develop approximately 7 days after exposure and commonly last >7 days.
    • Suspect when outbreaks of watery diarrhea in areas with contaminated water or food supply
  • Traveler’s diarrhea (TD) typically begins 3 to 7 days after arrival in foreign location and resolves within 5 days; rapid onset, generally self-limited


  • In resource-limited countries, acute diarrhea is more common in children; no age predilection in resource-rich countries
  • Acute diarrhea accounts for >128,000 U.S. hospital admissions and ~2.5 million annual deaths worldwide (1).
  • The WHO categorizes acute diarrhea (symptoms <14 days) into watery and bloody (dysentery) subtypes.


  • Fourth leading cause of death in children aged <5 years and eighth leading cause of death among all ages worldwide
  • Affects 11% of the general population
  • In resource-rich countries, acute diarrhea is largely due to contaminated food and water.

Etiology and Pathophysiology

  • Bacterial
    • Escherichia coli, Salmonella, Shigella, Campylobacter jejuni
    • Vibrio parahaemolyticus, Vibrio cholerae, Yersinia enterocolitica
    • Clostridium difficile, Staphylococcus aureus
    • Bacillus cereus, Clostridium perfringens
    • Listeria monocytogenes
    • Mycobacterium avium complex (in immunocompromised), Mycobacterium tuberculosis (in immunocompromised)
  • Viral
    • Rotavirus and Norovirus (most common)
    • Adenovirus
    • Astrovirus
    • Cytomegalovirus (CMV) (in immunocompromised)
  • Protozoal
    • Giardia lamblia, Entamoeba histolytica
    • Cryptosporidium (in immunocompromised)
    • Cystoisospora belli
    • Cyclospora, Microspora (in immunocompromised)
  • Pathophysiology (1)
    • Noninflammatory: most commonly viral; increased intestinal secretions without disruption of intestinal mucosa; watery character
    • Inflammatory: generally invasive or toxin-producing bacteria; disrupts mucosal integrity with subsequent tissue invasion/damage; bloody character
  • Viral diarrhea: changes in small intestine cell morphology, including villous shortening, increased number of crypt cells, and increased cellularity of the lamina propria
  • Bacterial diarrhea: Bacterial invasion of colonic wall leads to mucosal hyperemia, edema, and leukocytic infiltration.

Risk Factors

  • Travel to resource-limited countries
  • Failure to observe food/water precautions
  • Immunocompromised host (HIV, malignancy, chemotherapy)
  • Recent hospitalization
  • Antibiotic use
  • Proton pump inhibitor (PPI) use
  • Daycare exposure
  • Fecal-oral sexual contact
  • Nursing home residence
  • Pregnancy (12-fold increase for listeriosis) (1)

General Prevention

  • Frequent hand washing reduces incidence of diarrhea by approximately 30%.
  • Proper food and water precautions, particularly during foreign travel—“boil it, peel it, cook it, or forget it”
  • Avoid undercooked meat, raw fish, and unpasteurized milk.
  • Rotavirus vaccine (for infants)
  • Typhoid fever and cholera vaccine (for travel to endemic areas)
  • TD prevention:
    • Pretravel counseling on high-risk food/beverage
    • Consider daily prophylaxis with bismuth subsalicylate (BSS) in all travelers (can reduce the risk of TD by up to 60%); usual dosing of 2 tablets (262 mg each) or 2 oz (60 mL) liquid formulation 4 times daily
    • Do not use routine antibiotic prophylaxis.
    • When indicated (immunocompromised), the Infectious Disease Society of America recommends chemoprophylaxis with fluoroquinolones: norfloxacin 400 mg/day or ciprofloxacin 500 mg orally once or twice daily; otherwise, avoid given increasing global resistance to fluoroquinolones
    • Probiotics, prebiotics, and synbiotics have unclear benefit as prophylaxis.

Commonly Associated Conditions

  • Inflammatory bowel disease (IBD)
  • Immunocompromised (HIV, malignancy, chemotherapy)

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