Infective Etiologies of Acute Diarrhea in Children
Norovirus is now the leading viral cause of acute diarrhea in children under 5 years, accounting for approximately 1 million ambulatory visits annually, while rotavirus remains important in unvaccinated populations; among bacterial pathogens, Salmonella is the most common (42%), followed by Campylobacter (28%) and Shigella (21%). 1, 2
Viral Pathogens (Most Common Overall)
Norovirus has emerged as the predominant viral pathogen in the post-rotavirus vaccine era:
- Accounts for 58% of all foodborne gastroenteritis illnesses in children 1
- Responsible for nearly 1 million ambulatory care visits and 14,000 hospitalizations annually among children under 5 years 1
- Detection rates range from 9.7% to 18.1% in hospitalized children 3, 4, 5
Rotavirus remains a critical pathogen, particularly in unvaccinated populations:
- Historically caused 3 million annual episodes before vaccine introduction, with over 500,000 outpatient visits and 27,000 hospitalizations 1
- Still accounts for 25-35% of acute diarrhea cases in children under 5 years 1, 2, 6, 5
- Peak incidence occurs between 6 months and 2 years of age, with 72% of hospitalizations in the first 2 years of life 2
- Causes longer hospital stays and higher rates of vomiting compared to other viral pathogens 6
Other viral pathogens include:
- Adenovirus F 40/41: detected in 2.7-7% of cases 3, 6, 5
- Astrovirus: detected in 1.2-1.6% of cases 4, 5
- Sapovirus: detected in 4.4% of cases 5
Bacterial Pathogens (Second Most Common)
The five major bacterial pathogens collectively cause an estimated 291,000 illnesses, 103,000 physician visits, 7,800 hospitalizations, and 64 deaths yearly in children under 5 years 1:
- Salmonella enterica subspecies: 42% of bacterial cases, leading cause of hospitalization (35%) and death (28%) among bacterial pathogens 1
- Campylobacter: 28% of bacterial cases 1
- Shigella: 21% of bacterial cases 1
- Yersinia: 5% of bacterial cases 1
- E. coli O157 and other diarrheagenic E. coli: 3% for O157 specifically, but diarrheagenic E. coli collectively detected in 15-30% of cases 1, 3, 7
- Toxigenic Clostridium difficile: 16% of cases in some series 3
Parasitic Pathogens (Least Common)
- Giardia: 0.77-3% of cases 1, 7
- Cryptosporidium: 3.07% of cases 1, 7
- Entamoeba histolytica: rare in developed countries 1
Mixed Infections
Concurrent infections with multiple pathogens occur in 15-34% of cases, with higher rates in children under 2 years (65.9%) compared to older children 1, 3, 7:
- Most common combination is rotavirus with other viruses (89.2% of mixed infections) 5
- Mixed infections present with more severe symptoms, particularly higher rates of vomiting 5
Age-Specific Patterns
Children under 5 years have the highest disease incidence:
- Viral pathogens predominate in children under 5 years (38% vs 16% in older children) 1
- Bacterial pathogens peak in children 2-4 years of age 3
- First year of life accounts for 65% of hospitalizations and 85% of deaths 1
Clinical Pitfalls
Most acute diarrhea episodes are viral and self-limited, making routine laboratory testing unnecessary in previously healthy, immunocompetent children 1, 2. However, testing is warranted when:
- Bloody or mucoid stools suggest bacterial pathogens (Salmonella, Shigella, Campylobacter, STEC) 8
- Severe dehydration, altered mental status, or signs of shock are present 8, 9
- Immunocompromised status or outbreak situations exist 1
The mainstay of treatment is oral rehydration therapy regardless of etiology, as pathogen-specific treatment plays only a limited role 1, 2, 8.