How should acute norovirus gastroenteritis be diagnosed and managed, including rehydration, antiemetics, and infection‑control measures?

Norovirus Gastroenteritis: Diagnosis and Management

Immediate Clinical Approach

Norovirus gastroenteritis is a clinical diagnosis requiring no laboratory confirmation in typical cases; initiate oral rehydration therapy immediately and implement strict infection control measures, as no specific antiviral treatment exists. 1

Clinical Diagnosis

• Suspect norovirus when patients present with acute onset of vomiting and/or non-bloody diarrhea after a 12-48 hour incubation period, often accompanied by nausea, abdominal cramping, and low-grade fever. 1, 2

• Use the "rule out not norovirus" approach by excluding bacterial causes (bloody diarrhea, high fever >38.5°C, severe abdominal pain suggesting surgical abdomen) and considering epidemiologic context (outbreak setting, winter seasonality, multiple affected contacts). 3

• Laboratory confirmation is reserved for outbreak investigations only: collect whole stool specimens from at least 5 symptomatic individuals within 72 hours of symptom onset and use TaqMan-based real-time RT-PCR, which has 94% sensitivity and 92% specificity. 4, 1

Rehydration Strategy

Oral rehydration solution (ORS) is the cornerstone of treatment and should be started immediately:

• For mild dehydration (increased thirst, slightly dry mucous membranes): administer reduced osmolarity ORS at 50 mL/kg over 2-4 hours. 1

• For moderate dehydration (loss of skin turgor, dry mucous membranes): give 100 mL/kg ORS over 2-4 hours. 1

• For severe dehydration (altered consciousness, prolonged skin tenting, hypovolemic shock): treat as a medical emergency with immediate IV isotonic fluids in 20 mL/kg boluses, then transition to ORS once stabilized. 1

• Resume normal diet immediately after rehydration or during the rehydration process—do not withhold food. 1

Antiemetic Use

Antiemetics are not routinely recommended in guidelines for norovirus gastroenteritis. The focus remains on aggressive fluid replacement rather than symptom suppression, as vomiting typically resolves within 12-72 hours. 1, 5 In immunocompetent adults with nonbloody diarrhea, antimotility agents may be considered for self-treatment, but this applies more broadly to acute diarrhea rather than specifically to norovirus. 5

Infection Control Measures

Implement these measures immediately upon suspicion of norovirus:

• Handwashing with soap and running water for at least 20 seconds is mandatory—alcohol-based hand sanitizers (even ≥70% ethanol) cannot replace soap-and-water washing for norovirus decontamination, though they may be used as an adjunct. 1

• Isolate symptomatic patients until 24-48 hours after complete symptom resolution in institutional settings (hospitals, long-term care facilities, cruise ships). 1, 5

• Exclude symptomatic food handlers, childcare workers, and healthcare staff for 48-72 hours after symptom resolution to prevent transmission. 1, 5

• Environmental decontamination: First remove visible soil, then apply chlorine bleach solution at 1,000-5,000 ppm (approximately 1:50 to 1:10 dilution of household bleach) or EPA-approved disinfectant to all surfaces. 1

• Recognize presymptomatic transmission: infected persons may be contagious during the 24-48 hours before symptoms appear, making early isolation of exposed contacts critical in outbreak settings. 2

Expected Clinical Course

• In immunocompetent individuals, symptoms resolve within 12-72 hours (1-3 days) without specific therapy. 1, 2

• Prolonged illness lasting 4-6 days occurs more frequently in young children, elderly adults, and hospitalized patients. 1, 2

• Viral shedding peaks 2-5 days after infection and continues for an average of 4 weeks, though infectivity beyond the acute phase remains unclear—this prolonged shedding justifies extended work exclusion periods. 2, 5

High-Risk Populations Requiring Heightened Vigilance

Elderly patients in long-term care facilities face norovirus-related mortality risk and require aggressive monitoring for dehydration. 1

Immunocompromised patients (allogeneic stem cell transplant recipients, those on alemtuzumab or T-cell-depleting therapies, chronic lymphatic malignancies) may develop:

• Chronic norovirus diarrhea lasting months to years. 4, 1
• Mortality rates up to 25% in allo-SCT patients. 4, 2
• These patients warrant stool RT-qPCR during acute illness and evaluation for co-infections (Cryptosporidium, Cyclospora, microsporidia, Cystoisospora, CMV, MAC). 5

Common Pitfalls to Avoid

• Do not rely on alcohol-based hand sanitizers alone—norovirus is highly resistant and requires mechanical removal with soap and water. 1

• Do not allow premature return to work—the 48-72 hour post-symptom exclusion period is critical because viral shedding peaks after symptom onset. 1, 2

• Do not assume brief illness in all patients—elderly, pediatric, and hospitalized patients frequently experience 4-6 day courses, and vomiting/diarrhea persisting beyond one week warrants evaluation for alternative diagnoses. 1, 5

• Do not underestimate transmission potential—only 10-100 viral particles cause infection, transmission occurs via contact, aerosols, food, water, and environmental surfaces, and up to 30% of infections are asymptomatic yet still shed virus. 4, 2