What are the common causes of infectious gastroenteritis?

Common Causes of Infectious Gastroenteritis

Viral pathogens are the predominant cause of infectious gastroenteritis, with norovirus and rotavirus accounting for the vast majority of cases, followed by adenovirus and astrovirus. 1, 2

Primary Viral Pathogens

Norovirus

• Norovirus is now the leading cause of acute gastroenteritis across all age groups in developed countries, particularly in populations with rotavirus vaccination, causing nearly 1 million ambulatory care visits and 14,000 hospitalizations annually in the United States. 2
• Accounts for 58% of all gastroenteritis illnesses, far exceeding other pathogens in surveillance data. 2
• Affects all age groups except infants under 6 months, with peak transmission occurring December through February. 3
• Characterized by 12-48 hour incubation period followed by vomiting, watery diarrhea, and abdominal discomfort lasting 12-72 hours. 2, 4
• Highly contagious with as few as 10 viral particles capable of causing infection. 1

Rotavirus

• Rotavirus remains the most common cause of severe diarrhea in unvaccinated children, with approximately 3.5 million cases annually in the United States prior to widespread vaccination. 1
• Peak incidence occurs in children aged 6 months to 2 years, with seasonal concentration in cooler months (October-April). 1, 5
• Incubation period of approximately 2 days, followed by vomiting for 3 days and watery diarrhea lasting 3-8 days. 1
• Vomiting occurs in 80-90% of infected children but is typically brief, lasting 24 hours or less. 2
• Can cause severe dehydration requiring hospitalization, accounting for 35% of diarrheal hospital stays in children. 1

Adenovirus

• Enteric adenoviruses cause 1-10% of viral gastroenteritis outbreaks. 6
• Shows seasonal variation with peak transmission July through October. 3
• More commonly affects younger children and causes endemic disease rather than outbreaks. 7

Astrovirus

• Accounts for 0.5-5% of viral gastroenteritis outbreaks. 6
• Primarily affects young children and causes milder disease compared to rotavirus. 7
• Often detected in institutional settings such as day-care centers. 1

Epidemiologic Patterns

Endemic Disease (Primarily Children)

• Group A rotaviruses, enteric adenoviruses, astroviruses, and caliciviruses cause endemic diarrhea affecting all children worldwide in the first few years of life. 7
• These infections occur regardless of hygiene level, water quality, or sanitation practices. 7
• Infection typically provides immunity from severe disease upon reinfection (except for caliciviruses). 7

Outbreak Disease (All Ages)

• Norwalk-like viruses (noroviruses) cause epidemic viral diarrhea affecting people of all ages. 7
• Transmission occurs through fecally contaminated food or water, making them subject to public health control measures. 7
• Person-to-person transmission accounts for 38.1% of outbreaks, with 54.9% occurring in residential institutions. 6

Clinical Distinguishing Features

Viral vs. Bacterial Gastroenteritis

• Absence of blood in stool is the key distinguishing feature of viral gastroenteritis—bloody diarrhea suggests bacterial or parasitic etiology. 1, 4
• Common viral symptoms include: nausea (79%), abdominal cramps (71%), vomiting (69%), non-bloody diarrhea (66%), headache (50%), fever (37%), chills (32%), myalgias (26%). 1
• Vomiting is more prominent in viral gastroenteritis, occurring in up to 90% of pediatric cases. 2

High-Risk Settings for Transmission

Healthcare Facilities

• Nosocomial rotavirus is common in pediatric populations—all children hospitalized >2 weeks during rotavirus season may ultimately shed virus. 1, 5
• Rotavirus and norovirus outbreaks frequently occur in neonatal units, though full-term infants often have milder disease due to maternal antibodies. 1, 5

Day-Care Centers

• Both endemic and outbreak forms of rotavirus are common in day-care settings. 1, 5
• Asymptomatic viral shedding occurs in 50% of children the day before diarrhea starts and in one-third during the week after symptoms end. 1, 5

Special Populations at Risk

Immunocompromised Patients

• May experience prolonged viral shedding and chronic diarrhea. 2
• Rotavirus detected in 37% and adenovirus in 24% of HIV-positive patients with diarrhea. 1
• Mortality rates up to 25% reported in allogeneic stem cell transplant patients with norovirus. 2

Elderly

• At increased risk due to waning antibody levels and immunity with age. 1
• Diuretic medications and debility increase risk of adverse outcomes from dehydration. 1

Common Pitfalls

• Do not assume rotavirus is still the leading cause in vaccinated populations—norovirus has replaced it as the primary pathogen. 2
• Do not overlook asymptomatic transmission—viral shedding occurs before and after symptomatic periods. 1, 5
• Do not prescribe antibiotics—these are viral infections with no indication for antimicrobial therapy. 4