• Clinical science

Norovirus infection


Noroviruses are a frequent cause of viral gastroenteritis in individuals of all ages worldwide. Transmission commonly occurs from person to person, as well as through contact with contaminated surfaces, food, and water. Given their virulence and short incubation period, illnesses caused by noroviruses may quickly lead to outbreaks, which must be reported. The elderly, immunocompromised patients, and those who reside in long-term care facilities are at an increased risk of contracting the illness. The clinical presentation of norovirus infection includes acute-onset vomiting and watery diarrhea. Diagnosis can be confirmed with reverse transcription polymerase chain reaction (RT-PCR). Treatment is supportive and mainly involves fluid replacement therapy.


  • Peak incidence: November–March (winter months)
  • Community outbreaks (in nursing homes, hospitals, preschools, cruise ships, etc.) are common
  • Elderly and immunocompromised patients are commonly affected.
  • Most common cause of
    • Adult gastroenteritis
    • Severe acute gastroenteritis in children younger than 5 years of age
    • Foodborne illness


Epidemiological data refers to the US, unless otherwise specified.


  • Pathogen: Norovirus; is a non‑enveloped RNA calicivirus.
  • Transmission
    • Fecal‑oral route through contaminated food or water, person‑to‑person contact, via airborne droplets, and contact with contaminated surfaces
    • The virus is highly virulent.
    • Individuals are highly infectious during the acute phase and 24–72 hours following onset of symptoms

Viral pathogens in gastroenteritis (Rotavirus is a Reovirus, Norovirus is a Calicivirus): Rotate Reo, the calico cat off to Norway!


Clinical features

  • Incubation period: 12–48 hours
  • Nausea and acute-onset vomiting
  • Watery, non-bloody diarrhea
  • Abdominal cramps
  • Symptoms resolve after 48–72 hours.



  • Norovirus should be suspected in potentially exposed individuals if vomiting and/or diarrhea consisting ≥ 2 loose stools occur within a 24‑hour period.
  • Clinical suspicion of norovirus infection should be confirmed with reverse transcription PCR (RT-PCR).
    • Very sensitive method that can detect the virus from various specimens, including stool, vomit, food, and water.
  • Enzyme immunoassays: not a standard procedure due to low sensitivity (∼ 50%)


Differential diagnoses


The differential diagnoses listed here are not exhaustive.




Obligation to report

  • Health care providers are required to report all outbreaks.
  • Many cases go underreported, as symptoms are usually mild in healthy individuals → higher chance of further transmission