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Predicting Severe Outcomes in US Norovirus Outbreaks

J Infect Dis; ePub 2018 Nov 15; Burke, et al

Severe outcomes more frequently occurred in US norovirus outbreaks caused by GII.4 and those in healthcare settings, a recent study found. Acute norovirus outbreaks reported to the National Outbreak Reporting System (NORS) in 2009-2016 were linked to laboratory-confirmed norovirus outcomes reported to CaliciNet. Outbreaks were analyzed for differences in genotype, hospitalization, and mortality rates by timing, setting, transmission mode, demographics, clinical symptoms, and health outcomes. Among the findings:

  • 3,747 norovirus outbreaks were matched from NORS and CaliciNet.
  • GII.4 outbreaks (n=2,353) were associated with healthcare settings, winter months, and older age of cases (≥50% aged ≥75 years) in multivariable analysis.
  • Severe outcomes were more likely among GII.4 outbreaks.
  • Outbreaks in healthcare settings were also associated with higher hospitalization and mortality rates.


Burke RM, Shah MP, Wikswo ME, et al. The norovirus epidemiologic triad: Predictors of severe outcomes in US norovirus outbreaks, 2009–2016. [Published online ahead of print November 15, 2018]. J Infect Dis. doi:10.1093/infdis/jiy569.