Can norovirus cause bloody mucous stools?

Norovirus and Bloody Mucous Stools

Norovirus typically causes nonbloody diarrhea, but in rare cases it can trigger complications like ischemic colitis that may lead to bloody mucous stools. 1, 2

Clinical Presentation of Norovirus Infection

Norovirus infection is classically characterized by:

• Acute onset of symptoms after 12-48 hours incubation period
• Nonbloody diarrhea (typical presentation)
• Vomiting
• Nausea
• Abdominal cramps
• Low-grade fever and body aches in some cases
• Self-limiting illness lasting 1-3 days in healthy individuals (can extend to 4-6 days in vulnerable populations) 3, 1

Bloody Stools in Norovirus Infection

While norovirus typically presents with nonbloody diarrhea, there are documented cases where bloody stools can occur:

1. Secondary Ischemic Colitis: The most significant evidence comes from case reports where norovirus infection triggered ischemic colitis, resulting in bloody diarrhea. The pathophysiological mechanisms include:

   • Intensified intestinal peristalsis
   • Elevation of intraluminal gut pressure
   • Hypovolemia
   • Hemoconcentration 2

2. Inflammatory Bowel Disease (IBD) Exacerbation: Norovirus has been documented to trigger exacerbations of IBD, particularly ulcerative colitis, which can present with bloody mucous stools. In one study, 8 out of 9 IBD patients with norovirus presented with bloody diarrhea, and 6 required hospitalization 4

Risk Factors for Complicated Norovirus Infection

Certain populations are at higher risk for developing complications from norovirus:

• Immunocompromised patients: May develop chronic diarrhea lasting weeks to years 1, 5
• Elderly persons: Higher risk of severe disease and mortality 3, 1
• Young children: More susceptible to dehydration 1
• Patients with pre-existing IBD: May experience disease exacerbation with bloody stools 4

Diagnostic Considerations

When encountering a patient with bloody mucous stools and suspected norovirus:

1. Do not rule out norovirus solely based on the presence of bloody stools 2

2. Consider concurrent conditions:

   • Ischemic colitis
   • IBD exacerbation
   • Other bacterial or parasitic co-infections

3. Diagnostic testing:

   • Collect whole stool specimens during acute phase (≤72 hours from onset)
   • Use TaqMan-based real-time reverse transcription-PCR (RT-qPCR) for diagnosis 3
   • Consider endoscopic evaluation if bloody stools persist to rule out ischemic colitis or other causes

Management Approach

For patients with norovirus infection presenting with bloody mucous stools:

1. Rehydration: The cornerstone of treatment

   • Oral rehydration therapy for most patients
   • Intravenous fluids for severe dehydration or inability to tolerate oral fluids 1

2. Monitoring: More intensive for those with bloody stools

   • Electrolyte balance
   • Signs of worsening dehydration
   • Evidence of colitis or other complications

3. Supportive care:

   • Anti-emetics for severe vomiting may be considered
   • Avoid anti-diarrheal medications, especially in children 1

4. Infection control:

   • Proper hand hygiene with soap and water (alcohol-based sanitizers are less effective)
   • Environmental cleaning with chlorine bleach solution or EPA-approved disinfectants
   • Isolation measures for 24-48 hours after symptom resolution 1

Important Caveats

• The presence of bloody stools should prompt consideration of other diagnoses or complications
• Physicians should not exclude viral gastroenteritis simply due to bloody diarrhea 2
• Norovirus is highly contagious, with an estimated infectious dose as low as 18 viral particles 3
• Chronic norovirus infection is the major sequela in immunocompromised patients 5