Norovirus Incubation Period
Symptoms of norovirus typically occur 12-48 hours after ingestion, with illness beginning after this incubation period and characterized by acute onset of vomiting, diarrhea, nausea, and abdominal cramps. 1
Timing of Symptom Onset
- The incubation period for norovirus is consistently reported as 12-48 hours across multiple CDC guidelines 1
- This timeframe is also described as 24-48 hours in older guidelines, representing the same clinical window 1
- The illness begins with acute onset of symptoms following this incubation period, meaning symptoms develop rapidly once they start 1
Clinical Presentation After Incubation
Once the incubation period passes, patients experience:
- Vomiting and diarrhea as the predominant symptoms, with some persons experiencing only one or the other 1
- Nausea and abdominal cramps accompanying the gastrointestinal symptoms 1
- Low-grade fever and body aches may also occur, leading to the colloquial term "stomach flu" 1
Duration and Recovery
- In immunocompetent individuals, symptoms typically last 12-72 hours with self-resolution 2
- The median duration is 2 days for healthy adults and healthcare workers, with 75% achieving complete recovery within 3 days 3
- Hospitalized patients experience longer illness duration (median 3 days, with 75% recovering within 5 days), which is significantly longer than other populations 3
- More prolonged courses of 4-6 days can occur in young children, elderly persons, and hospitalized patients 1
Special Populations
Immunocompromised patients represent a critical exception to the typical course:
- These patients can experience prolonged infection lasting months to years 2, 4
- Complications include severe malnutrition, villous atrophy, and continuous viral shedding 2, 4
- Mortality rates up to 25% have been reported in allogeneic stem cell transplant patients 1, 2
Transmission Considerations
- The virus requires only 10-100 viral particles to cause infection, making it highly contagious 1
- Peak viral shedding occurs 2-5 days after infection, with approximately 100 billion viral copies per gram of feces 1
- Viral shedding can continue for an average of 4 weeks following infection, though infectivity beyond the acute phase is unclear 1
- Up to 30% of infections are asymptomatic, yet these individuals can still shed virus at lower titers 1