What are the symptoms of norovirus?

Norovirus Symptoms

Norovirus infection is characterized by acute onset of nonbloody diarrhea, vomiting, nausea, and abdominal cramps, with symptoms typically appearing 12-48 hours after exposure and resolving without treatment after 1-3 days in healthy individuals. 1

Primary Symptoms

• Gastrointestinal manifestations:

  • Vomiting (94% of cases) 2
  • Diarrhea (81% of cases) 2
  • Nausea
  • Abdominal cramps/pain

• Systemic symptoms:

  • Low-grade fever (66% of cases) 2
  • Body aches/myalgia 1, 3
  • Headache 4
  • Malaise 4

Clinical Presentation Patterns

Norovirus infection typically presents in two main clinical patterns:

1. Gastroenteritis with fever (47% of cases)
2. Gastroenteritis without fever (30% of cases) 2

Notably, approximately 19% of cases may present without diarrhea, with vomiting as the predominant symptom 2. Some individuals may experience only vomiting or only diarrhea 1.

Symptom Severity and Duration

• Typical duration: 1-3 days in healthy individuals 1, 3
• Extended duration: 4-6 days in vulnerable populations (young children, elderly persons, hospitalized patients) 1, 3
• Vomiting intensity: Repeated vomiting (≥4 times/day) is common 2
• Diarrhea: Usually watery, non-bloody 4

Distinguishing Features from Other Viral Gastroenteritis

When compared to rotavirus infection:

• Norovirus tends to cause less intense fever (66% vs 97% for rotavirus) 2
• High fever (>38°C) is less common with norovirus (48% vs 81% for rotavirus) 2
• Norovirus causes less intense diarrhea but more frequent vomiting episodes 2

High-Risk Populations and Complications

• Elderly individuals: Higher risk of severe dehydration and mortality, particularly in long-term care facilities 1, 3
• Young children: More susceptible to dehydration requiring careful monitoring 3
• Immunocompromised patients: May experience prolonged illness lasting weeks to years with potential complications including:
  • Chronic diarrhea
  • Villous atrophy
  • Severe malnutrition
  • Continuous viral shedding 3

Approximately 10% of persons with norovirus gastroenteritis seek medical attention, which may include hospitalization and treatment for dehydration with oral or intravenous fluid therapy 1.

Clinical Pitfalls

• Norovirus is often mistakenly called "stomach flu" despite having no biological association with influenza 1
• Asymptomatic infections can occur in up to 30% of cases, but these individuals can still shed the virus and potentially transmit infection 1
• The highly contagious nature of norovirus (as few as 20 viral particles can cause infection) 5 means that symptoms may rapidly spread through households, healthcare facilities, and other group settings

Early recognition of symptoms and prompt implementation of appropriate infection control measures are essential to prevent outbreaks, particularly in healthcare and institutional settings.