Acute diarrhea and/or vomiting which typically lasts <14 days. Mild illness with vomiting is likely due to a viral etiology. Severe illness with fevers, severe dehydration, severe abdominal pain, and bloody stools are more likely due to a bacterial illness. However, viruses may also lead to serious illnesses leading to hospitalization and/or death. Parasites may produce a prolonged diarrheal illness.



  • The incidence of acute gastroenteritis (AGE) in the United States is approximately 0.6 episodes per person per year or an estimated 179 million episodes in the United States, leading to 496,000 hospitalizations and ~5,000 deaths (1).
  • Diarrheal illnesses account for 15% of all deaths in children <5 years old and cause approximately 1.4 million children deaths annually in developed countries (2).
  • Increased numbers of AGE outbreaks aboard cruise ships have been reported in the past decade.

Etiology and Pathophysiology

  • Viral illnesses account for 75–90% of AGE in developed countries. Norovirus is the most common cause in adults. Rotavirus is the most common cause in infants and children. Other viruses include adenovirus and astrovirus. Viruses are easily transmissible from person to person and also commonly cause malaise, fatigue, myalgias, and headaches. Hepatitis A is common in areas with poor sanitation and is transferred by the fecal–oral route.
  • Bacterial illnesses account for 10–15% of AGE in developed countries and generally occur by consuming contaminated or improperly prepared food or contaminated water, especially during travel. The most common bacterial causes of gastroenteritis in the United States include Salmonella species, Campylobacter jejuni, Escherichia coli, and Shigella species. Other bacteria include Staphylococcus aureus, Listeria, and Yersinia. Bacterial pathogens or their toxins commonly invade the colonic mucosa and may cause gastrointestinal bleeding, high fevers, severe abdominal pain, and sepsis. Clostridium difficile is an emerging pathogen that is most commonly a nosocomial infection in those who are prescribed antibiotics while hospitalized over 3 days. Pregnant women who consume deli meats, soft cheese, or raw milk are at risk for Listeria. Vibrio cholerae is pandemic in developing nations with contaminated water sources including sub-Saharan Africa and Asia. Preformed toxins from Bacillus cereus (associated with reheated rice) or S. aureus (undercooked meat) cause sudden abdominal cramping and vomiting within a few hours of consuming infected food. Scombroid (histamine contained in spoiled seafood) causes gastroenteritis with allergic symptoms within several minutes of consumption.
  • Parasites are relatively rare in developed countries. Parasites include Giardia lamblia, Cyclospora, Entamoeba histolytica, and Cryptosporidium and may be found in travelers to third-world nations and in men who have sex with men (MSM). Giardia is also found in local travelers who drink water from natural sources, children in daycares, and daycare workers.

Risk Factors

  • Exposure to infected persons. Viral pathogens are easily transmissible from person to person.
  • Risk factors for severe disease include:
    • Infants <6 months old
    • Children in daycare (high incidence of Giardia and Shigella)
    • Poor nutrition status
    • Frailty
    • Travel
    • Antibiotic use within the last 3 months
    • Recent hospitalization
    • Patients who are immunocompromised
    • Patients with comorbidities
    • Pregnancy
    • MSM
    • Chronic proton pump inhibitor (PPI) use

General Prevention

  • Frequent hand washing
  • Good hygiene
  • Avoidance of sick contacts
  • Proper food handling and cooking
  • Drinking clean water
  • Routine immunizations (rotavirus)
  • Immunizations for travelers (Salmonella typhi)

Commonly Associated Conditions

  • Hemolytic uremic syndrome (HUS): caused by a Shiga-like toxin produced most commonly by enterotoxigenic E. coli 0157:H7 (STEC) but also by other serotypes of E. coli, Shigella, or Campylobacter, which includes a hemolytic anemia, acute renal failure, and thrombocytopenia
  • Guillain-Barré syndrome: caused by autoantibody attack of the peripheral nervous system, rarely seen after a Campylobacter infection
  • Necrotizing enterocolitis (NEC) in neonates
  • Mallory-Weiss tears with severe, forceful vomiting

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