What are the causes of diarrhea and vomiting in vulnerable populations, including the elderly, young children, and those with underlying medical conditions?

Causes of Diarrhea and Vomiting in Vulnerable Populations

In vulnerable populations including the elderly, young children, and immunocompromised patients, infectious causes dominate—with rotavirus and enteric viruses predominating in young children (especially during winter months), while bacterial pathogens (Salmonella, Shigella, Campylobacter, enterotoxigenic E. coli) and parasites (Cryptosporidium, Giardia) affect all age groups, though mortality disproportionately impacts the elderly who account for 51-85% of diarrhea-related deaths despite lower incidence rates. 1

Age-Specific Etiologic Patterns

Young Children (<3 Years)

• Viral pathogens are the leading cause, with attack rates of 2.46 illnesses per year per child under 3 years old—the highest of any age group 1

• Rotavirus and other enteric viruses predominate with seasonal peaks in winter months, accounting for the majority of pediatric gastroenteritis cases 1

• Norovirus causes both diarrhea and vomiting, with vomiting without diarrhea occurring in 35% of cases among children under 2 years, making it a significant cause of acute gastroenteritis in this age group 2

• Bacterial causes include enterotoxigenic E. coli (ST-ETEC), Shigella, Cryptosporidium, and typical enteropathogenic E. coli, which are associated with increased mortality risk in infants and toddlers 3

• Four pathogens account for most attributable cases of moderate-to-severe diarrhea globally: rotavirus, Cryptosporidium, ST-ETEC, and Shigella 3

Elderly Patients (≥60-75 Years)

• While elderly patients have lower incidence rates than children, they account for 51% of all diarrheal deaths (patients ≥74 years old), with 85% of mortality associated with diarrhea involving those over 60 years 1

• Bacterial pathogens predominate in this population, including Salmonella, Shigella, Campylobacter jejuni, and Clostridium difficile (particularly following antibiotic exposure) 1, 4

• Foodborne infections cause an estimated 5,000 deaths annually in the United States, with most occurring in elderly patients 1

• The elderly experience 25% of all hospitalizations related to diarrhea despite representing a smaller proportion of total cases 1

Immunocompromised Patients

• Immunosuppressed patients face prolonged and more severe illness lasting weeks rather than days, with higher risk of complications and death 5, 6

• Opportunistic pathogens become significant causes, including Cryptosporidium (associated with 2.3-fold increased mortality risk in toddlers), Mycobacterium avium complex, microsporidia, Cyclospora, and Isospora 1, 7

• Bacterial causes require more aggressive evaluation and treatment, as empirical antibiotics are indicated for invasive diarrhea in this population even when not routinely recommended in immunocompetent patients 6

Common Infectious Etiologies Across All Vulnerable Groups

Viral Causes

• Rotavirus remains a leading cause globally with symptoms typically resolving within 3-8 days (vomiting within 24 hours, diarrhea persisting 3-7 days) 5

• Norovirus causes acute illness lasting 12-72 hours but remains infectious for up to 2 days after symptom resolution, facilitating transmission 5

• Norwalk-like viruses are increasingly recognized in developed countries as common causes of gastroenteritis 4

Bacterial Causes

• Enterotoxigenic E. coli (ST-ETEC) predominates in developing areas and is associated with 1.9-fold increased mortality risk in infants aged 0-11 months 3, 4

• Shigella causes invasive dysentery characterized by bloody diarrhea, high fever (>38.5°C), and systemic toxicity, requiring antimicrobial therapy 1, 3

• Salmonella and Campylobacter jejuni are found worldwide, with Salmonella causing foodborne outbreaks and both organisms potentially mimicking appendicitis clinically 1, 7, 4

• Clostridium difficile is increasingly common in developed countries, particularly following antibiotic exposure, and causes severe colitis with inflammation 1, 4

• Vibrio cholerae O1 and Aeromonas are important in selected geographic sites and specific epidemiologic settings 3

Parasitic Causes

• Cryptosporidium is found throughout the world and is associated with 2.3-fold increased mortality risk in toddlers aged 12-23 months 1, 3, 4

• Giardia lamblia causes diarrhea globally and requires specific testing with fluorescence or EIA for detection 1, 4

• Parasitic causes are generally more common in subtropical areas but can occur anywhere, particularly in immunocompromised hosts 6, 4

Epidemiologic Risk Factors Pointing to Specific Causes

• Travel to developing areas suggests enterotoxigenic E. coli, Shigella, or parasitic infections as likely etiologies 1

• Day-care center attendance or employment increases risk of rotavirus, norovirus, Giardia, and Shigella transmission 1

• Consumption of unsafe foods (raw meats, eggs, shellfish, unpasteurized products) or untreated water points to Salmonella, Campylobacter, or parasitic causes 1

• Recent antibiotic use strongly suggests Clostridium difficile as the causative pathogen 1, 4

• Winter seasonality indicates viral etiologies (rotavirus, norovirus) as the predominant cause 1

• Known outbreaks in dormitories, offices, or social functions suggest norovirus or other highly transmissible viral pathogens 1

Critical Mortality Considerations

• Most deaths globally occur in young children in developing areas (3.1 million deaths annually, 18,400 per day), while in the United States most deaths occur in elderly patients (3,171 deaths annually, with 51% in those ≥74 years) 1

• Odds of dying are 8.5-fold higher in children with moderate-to-severe diarrhea compared to controls, with 87.9% of deaths occurring during the first 2 years of life 3

• Dehydration and malnutrition are the major complications causing death, particularly in young children, elderly patients, and immunosuppressed individuals 6

• Premature infants face higher risk for severe, prolonged illness due to lack of maternal antibodies 5