Most Common Type of Diarrheal Illness by Geographic Location
United States and Developed Countries
In the United States and other developed countries, viral gastroenteritis is the most common cause of acute diarrheal illness, with rotavirus historically accounting for approximately 25% of all acute diarrhea cases in children and norovirus increasingly dominant in vaccinated populations. 1, 2, 3
Age-Specific Patterns in Developed Settings
Children under 5 years: Rotavirus remains the leading cause of severe diarrheal disease requiring hospitalization, responsible for 30-50% of diarrhea hospitalizations in this age group, though norovirus has become increasingly important after widespread rotavirus vaccination 1
Adults: Viral gastroenteritis (primarily norovirus) is the most common etiology, representing a self-limited disease in most cases 2, 3
Peak incidence for rotavirus: Occurs between 6 months and 2 years of age, with 72% of hospitalizations in the first 2 years of life 1
Bacterial Causes in Developed Countries
Bacterial pathogens account for a smaller proportion but are important for severe or bloody diarrhea, with Salmonella being the most common bacterial cause, followed by Campylobacter, Shigella, and certain E. coli strains 1
Foodborne bacterial illnesses account for 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths annually in the United States 4
Developing Countries and Tropical Regions
In developing countries and tropical regions, bacterial diarrhea with invasive or toxigenic mechanisms predominates, particularly in hot climates, with rotavirus causing the highest burden of severe disease in children. 5
Key Pathogens in Resource-Limited Settings
Rotavirus: Causes approximately 3 million annual episodes of acute gastroenteritis in children under 5 years before vaccine introduction, with virtually all children becoming infected in the first 3-5 years of life 1
Bacterial pathogens: More frequent than in developed countries, especially invasive organisms causing dysentery (Shigella, Campylobacter) 4, 5
Cholera: Remains a significant concern in endemic areas, particularly in refugee and displaced populations 4
Travelers' Diarrhea
Travelers to developing countries most commonly develop bacterial diarrhea, with enterotoxigenic E. coli being the predominant pathogen, though persistent diarrhea occurs in approximately 3% of travelers. 4, 6
Specific Travel-Related Considerations
Bacterial causes (especially toxigenic E. coli) are more common than viral causes in travelers to tropical and subtropical regions 5
Persistent diarrhea (≥14 days) in travelers is caused by different pathogens than acute illness, including Giardia, Cryptosporidium, and enteroaggregative E. coli 6
Schistosoma mansoni intestinal infection occurs only in endemic areas and is uncommon even there 6
Nosocomial (Hospital-Acquired) Diarrhea
Clostridium difficile is the predominant cause of nosocomial diarrhea occurring ≥3 days after hospitalization. 4
C. difficile should be specifically tested for in patients with recent antibiotic therapy or healthcare exposure 4
Many commercial enzyme immunoassays are available for C. difficile toxin detection 4
Clinical Implications for Diagnosis
When to Pursue Diagnostic Testing
Diagnostic evaluation should be reserved for patients with: severe dehydration, persistent fever, bloody or mucoid stools, immunosuppression, recent hospitalization, or diarrhea lasting >1 day with fever or systemic illness. 4, 2, 3
Most episodes of acute watery diarrhea in developed countries are uncomplicated, self-limited, and require only supportive treatment without laboratory workup 2, 3
Routine stool cultures are not recommended for typical acute watery diarrhea 2
Geographic-Specific Testing Priorities
Developed countries: Molecular studies (multiplex PCR) are preferred over traditional stool cultures unless an outbreak is suspected 3
Tropical/endemic areas: Blood cultures for enteric fever (typhoid), malaria screening for febrile illness, and consideration of parasitic causes 7
Refugee/displaced populations: Surveillance for cholera with rectal swabs in Cary-Blair transport medium when outbreak suspected 4
Common Pitfalls to Avoid
Do not delay rehydration while pursuing diagnostic testing—oral rehydration therapy should be initiated immediately for any significant diarrheal illness 4
Avoid antimotility agents in patients with bloody diarrhea or proven Shiga toxin-producing E. coli infection, as they may worsen outcomes 4, 2
Do not routinely prescribe antibiotics for uncomplicated watery diarrhea, as most cases are viral and self-limited; empiric antibiotics are rarely warranted except in sepsis or specific travel scenarios 2, 3
Consider factitious diarrhea (laxative abuse) in patients with extensive negative workup, as this accounts for up to 20% of cases at tertiary referral centers 4