What is the initial approach to managing norovirus infection presenting with watery diarrhea?

Management of Norovirus-Induced Watery Diarrhea

For most immunocompetent patients with suspected norovirus causing watery diarrhea, no diagnostic workup is needed—focus immediately on oral rehydration therapy and supportive care without laboratory testing or antimicrobial therapy. 1

When Diagnostic Testing IS Indicated

Diagnostic workup for norovirus should be pursued only in specific high-risk scenarios:

• Immunocompromised patients (organ transplant recipients, HIV/AIDS, chemotherapy patients, immunosuppressive therapy) presenting with watery diarrhea should have stool specimens collected during the acute phase (≤72 hours from onset) for RT-qPCR testing 1
• Outbreak settings (long-term care facilities, hospitals, cruise ships, schools) require collection of whole stool specimens from at least five persons during acute illness for RT-qPCR diagnosis and genotyping, with results reported to CDC via CaliciNet 1
• Elderly patients >90 years in long-term care facilities warrant evaluation given their 20-30% increased risk of death and hospitalization during norovirus outbreaks 1
• Patients with symptoms persisting beyond 7 days should be evaluated for volume status and alternative diagnoses, though empiric treatment should be avoided in persistent watery diarrhea lasting ≥14 days 1

Core Management Strategy for All Patients

Immediate Rehydration (First Priority)

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

• Prescribe ORS containing 65-70 mEq/L sodium and 75-90 mmol/L glucose as first-line therapy for mild to moderate dehydration 1, 2
• Target 2200-4000 mL/day total fluid intake, with administration rate exceeding ongoing losses (urine output + 30-50 mL/h insensible losses + stool losses) 2
• Continue ORS until clinical dehydration is corrected and diarrhea resolves 1, 2
• For mild illness, diluted fruit juices, flavored soft drinks with saltine crackers, and broths can supplement but commercial ORS is superior 2

Escalate to intravenous fluids if:

• Severe dehydration with altered mental status, shock, or hypotension develops 1, 2
• Patient cannot tolerate oral intake 1
• Ileus is present 1
• Use isotonic fluids (lactated Ringer's or normal saline) and continue until pulse, perfusion, and mental status normalize 1, 2

Symptomatic Management

Loperamide may be used cautiously in immunocompetent adults:

• Start 4 mg initially, then 2 mg every 2-4 hours or after each unformed stool, maximum 16 mg daily 2, 3
• Absolutely contraindicated if fever or bloody stools are present due to risk of toxic megacolon 2, 3
• Avoid in children under 18 years 2
• Use caution in elderly patients, especially those taking QT-prolonging medications (Class IA or III antiarrhythmics) 3

Dietary Approach

• Resume normal age-appropriate diet immediately or as soon as rehydration is complete 1, 2
• Continue human milk feeding in infants throughout the illness 1
• Small, light meals initially, avoiding fatty, heavy, spicy foods and caffeine 2

What NOT to Do

Antimicrobial therapy is NOT indicated:

• The IDSA strongly recommends against empiric antibiotics for acute watery diarrhea without recent international travel in immunocompetent patients 1
• Norovirus is self-limited and requires no specific antiviral therapy 4
• Asymptomatic contacts should not receive empiric or preventive therapy 1

Laboratory testing is NOT routinely needed:

• In the absence of an outbreak, residents with symptoms consistent with small bowel infection and stable clinical status should be evaluated for volume assessment only, with no laboratory evaluation required unless severely ill or symptoms persist beyond 7 days 1

Special Considerations for Immunocompromised Patients

This population requires a fundamentally different approach:

• Obtain stool specimens for RT-qPCR during acute phase as norovirus can cause chronic, severe infection lasting months to years 1, 5, 6
• Evaluate for additional opportunistic pathogens: Cryptosporidium, Cyclospora, microsporidia, Cystoisospora belli, CMV, and MAC 1
• Consider blood cultures for MAC and colonoscopy with biopsy for CMV enteritis if diarrhea persists 1
• Chronic norovirus infection can cause villous atrophy leading to severe malnutrition, dehydration, and continuous viral shedding 6, 7
• Experimental treatments (nitazoxanide, ribavirin, enterally administered immunoglobulin) have been reported in case series but lack definitive evidence 6

Infection Control Measures

Critical for outbreak prevention and management:

• Isolate ill patients until 24-48 hours after complete symptom resolution in institutional settings 1, 4
• Exclude ill healthcare workers, food handlers, and childcare workers until 48-72 hours after symptom resolution 1, 4
• Promote handwashing with soap and running water for minimum 20 seconds—alcohol-based sanitizers are adjunctive only and should not substitute for soap and water 1, 4
• Disinfect environmental surfaces with chlorine bleach solution 1000-5000 ppm (1:50 to 1:10 dilution of household bleach) or EPA-approved disinfectant after initial cleaning 1
• Recognize that very small numbers of viral particles (as few as 18) are infectious and can be transmitted by direct contact, fomites, or aerosolized vomitus 1

Expected Clinical Course

• Incubation period: 12-48 hours after exposure 1, 4
• Symptom duration in immunocompetent individuals: typically 12-72 hours with self-resolution 4
• Longer courses of 4-6 days can occur in young children, elderly, and hospitalized patients 4
• Peak viral shedding occurs 2-5 days after infection, with shedding continuing for average of 4 weeks following infection 4

Critical Pitfalls to Avoid

• Never neglect rehydration while focusing on other interventions—dehydration causes the morbidity and mortality, not the diarrhea itself 2
• Never use loperamide when fever or bloody stools are present due to risk of toxic megacolon 2, 3
• Never assume brief illness in immunocompromised patients—they can have chronic infection lasting months to years requiring isolation throughout 1, 6, 7
• Never rely on alcohol-based hand sanitizers alone—vigorous handwashing with soap and water is essential as alcohol may not completely inactivate norovirus 1
• Never wait for laboratory confirmation before initiating supportive care—clinical diagnosis is sufficient in typical presentations 1, 4