Diarrhea, Acute

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  • An abnormal increase in stool water content, volume, or frequency (≥3 in 24 hours) for <14 days duration
  • 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 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.
    • Suspect Clostridium difficile in patients with recent antibiotic use or hospitalization.
  • 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 developing countries, acute diarrhea is more common in children; no age predilection in developed countries
  • Acute diarrhea accounts for >128,000 U.S. hospital admissions and ~1.5 million annual deaths worldwide (1).

  • Second leading cause of death in children <5 years and seventh leading cause of death among all ages worldwide
  • Affects 11% of the general population
  • Rotavirus and adenovirus most common in children <2 years, bacteria are more common in children >2 years
  • In developing world, acute diarrhea is largely due to contaminated food and water (1).

Etiology and Pathophysiology

  • Bacterial
    • Escherichia coli
    • Salmonella, Shigella, Campylobacter jejuni
    • Vibrio parahaemolyticus, Vibrio cholerae
    • Yersinia enterocolitica
    • C. difficile
    • Staphylococcus aureus
    • Bacillus cereus
    • Clostridium perfringens
    • Listeria monocytogenes
  • Viral
    • Rotavirus and Norovirus (most common)
    • Adenovirus
    • Astrovirus
    • Cytomegalovirus (in immunocompromised)
  • Protozoal
    • Giardia lamblia
    • Entamoeba histolytica
    • Cryptosporidium
    • Isospora belli
    • Cyclospora, Microspora
  • Pathophysiology (1)
    • Noninflammatory: most commonly viral; increased intestinal secretions without disruption of intestinal mucosa; watery
    • Inflammatory: generally invasive or toxin-producing bacteria; disrupts mucosal integrity with subsequent tissue invasion/damage; bloody stools
  • 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 developing countries
  • Failure to observe food/water precautions
  • Immunocompromised host
  • 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; hand washing promotion may reduce 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, unpasteurized milk.
  • Rotavirus vaccine (for infants)
  • Typhoid fever and cholera vaccine (for travel to endemic areas)
  • TD prophylaxis
    • 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
      • Antibiotic prophylaxis should not be routinely used.
      • IDSA recommends chemoprophylaxis with fluoroquinolones: norfloxacin 400 mg/day or ciprofloxacin 500 mg orally once or twice daily. Fluoroquinolones are not recommended for prophylaxis by the International Society of Travel Medicine, which advocates the use of rifaximin 200 mg once or twice daily (2)[C]
      • Probiotics, prebiotics, and synbiotics have unclear benefit as prophylaxis.

Commonly Associated Conditions

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

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