Causes of Gastroenteritis

Viral pathogens are the most common cause of gastroenteritis, followed by bacteria and parasites. 1

Viral Causes

Rotavirus: The most common cause of severe diarrhea among children. In the United States, approximately 3.5 million cases occur each year. By age 4, most children have been infected and developed immunity to severe disease. Peak incidence is among children 6 months to 2 years of age. 2
Norovirus: The most common viral cause of gastroenteritis outbreaks among adults. Norovirus and Salmonella are the leading pathogens among the 24 gastroenteritis pathogens transmissible by food in the United States. 2
Enteric adenoviruses: Primarily serotypes 40 and 41, contributing to 5-20% of hospitalizations for childhood diarrhea in developed countries. Peak incidence is among children less than 2 years of age. 2
Calicivirus: Affects people of all ages, though historically thought to primarily affect children, with attack rates in outbreaks ranging from 50% to 70%. 3
Astrovirus: One of the common viral pathogens affecting the gastrointestinal tract, particularly in children. 2, 4
Sapovirus: Characterized by an incubation period of 1-3 days, with illness typically lasting 4 days. Common symptoms include vomiting, diarrhea, and upper respiratory symptoms. 3

Pestivirus: Identified in 23% of specimens from children less than 2 years of age with gastroenteritis of unknown etiology in one study on an Arizona Indian reservation. 2
Picobirnavirus: Documented in human cases of diarrhea in Brazil, though previously thought to cause diarrhea only in animals. 2
Parvovirus-like particles: Identified in stool specimens and associated with shellfish-related outbreaks of gastroenteritis. 2
Torovirus: Known causes of diarrhea among cattle, with identification reported in human specimens. 2
Coronavirus: Well-established causes of diarrhea in animals and respiratory disease in humans. Since the pandemic in 2019, coronavirus gastroenteritis has increased in incidence and prevalence. 2, 4

Salmonella enterica subspecies: One of the leading bacterial causes of gastroenteritis, exceeding norovirus as a cause of hospitalization (35% vs 28%) and death (28% vs 11%). 2
Campylobacter: A common bacterial pathogen causing gastroenteritis, accounting for approximately 28% of bacterial gastroenteritis cases in children under 5 years. 2
Shigella: Accounts for about 21% of bacterial gastroenteritis cases in children under 5 years in the United States. 2
Yersinia and E. coli O157: Less common bacterial causes, accounting for 5% and 3% of bacterial gastroenteritis cases in children under 5 years, respectively. 2
Clostridioides difficile: Increasing in prevalence in both adult and pediatric patients, particularly associated with antibiotic use. 5

In outbreaks of viral gastroenteritis, common symptoms include: nausea (79%), abdominal cramps (71%), vomiting (69%), diarrhea (never bloody) (66%), headache (50%), fever (37%), chills (32%), myalgias (26%), and sore throat (18%). 2
For Norwalk virus outbreaks, the average incubation period is 24-48 hours and the average duration of illness is 12-60 hours. 2
Transmission routes include:
- Person-to-person contact (fecal-oral route) 2, 3
- Contaminated food and water 2, 3
- Aerosol transmission (particularly for norovirus) 2
- Fomites (contaminated surfaces) 2
Viral shedding often occurs before symptoms appear and continues after symptoms resolve, facilitating transmission. For rotavirus, asymptomatic excretion has been reported among half of children the day before diarrhea starts and among one-third during the week after symptoms end. 2

Hand hygiene: Proper handwashing with soap and water for at least 20 seconds is essential to prevent transmission. 3
Surface disinfection: Proper disinfection of contaminated surfaces with chlorine bleach solution. 3
Food safety: Exclusion of ill food handlers until 48-72 hours after symptom resolution. 3
Isolation: Isolation of ill residents in institutional settings for 24-48 hours after symptom resolution. 3
Vaccination: Rotavirus vaccination has significantly reduced the burden of rotavirus disease, decreasing infections by as much as 90% in children. 1

Outbreaks in closed environments: Nursing homes, cruise ships, and other closed environments facilitate prolonged transmission of gastroenteritis pathogens. 2
Immunocompromised patients: Viral gastroenteritis can be more severe and prolonged in immunocompromised individuals. Herpes virus and cytomegalovirus can cause ulcerative GI disease with bloody diarrhea in these patients. 4
Age considerations: The elderly and very young are at highest risk for severe outcomes from gastroenteritis, including dehydration and death. 6