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. 2019 Apr 16;219(9):1364-1372.
doi: 10.1093/infdis/jiy569.

The Norovirus Epidemiologic Triad: Predictors of Severe Outcomes in US Norovirus Outbreaks, 2009-2016

Rachel M Burke  1   2 , Minesh P Shah  1   2 , Mary E Wikswo  1 , Leslie Barclay  1 , Anita Kambhampati  1   3 , Zachary Marsh  1   4 , Jennifer L Cannon  5 , Umesh D Parashar  1 , Jan Vinjé  1 , Aron J Hall  1
Affiliations

The Norovirus Epidemiologic Triad: Predictors of Severe Outcomes in US Norovirus Outbreaks, 2009-2016

Rachel M Burke et al. J Infect Dis. .

Abstract

Background: Noroviruses are the leading cause of acute gastroenteritis outbreaks worldwide. Clarifying the viral, host, and environmental factors (epidemiologic triad) associated with severe outcomes can help target public health interventions.

Methods: Acute norovirus outbreaks reported to the National Outbreak Reporting System (NORS) in 2009-2016 were linked to laboratory-confirmed norovirus outbreaks reported to CaliciNet. Outbreaks were analyzed for differences in genotype (GII.4 vs non-GII.4), hospitalization, and mortality rates by timing, setting, transmission mode, demographics, clinical symptoms, and health outcomes.

Results: A total of 3747 norovirus outbreaks were matched from NORS and CaliciNet. Multivariable models showed that GII.4 outbreaks (n = 2353) were associated with healthcare settings (odds ratio [OR], 3.94 [95% confidence interval {CI}, 2.99-5.23]), winter months (November-April; 1.55 [95% CI, 1.24-1.93]), and older age of cases (≥50% aged ≥75 years; 1.37 [95% CI, 1.04-1.79]). Severe outcomes were more likely among GII.4 outbreaks (hospitalization rate ratio [RR], 1.54 [95% CI, 1.23-1.96]; mortality RR, 2.77 [95% CI, 1.04-5.78]). Outbreaks in healthcare settings were also associated with higher hospitalization (RR, 3.22 [95% CI, 2.34-4.44]) and mortality rates (RR, 5.65 [95% CI, 1.92-18.70]).

Conclusions: Severe outcomes more frequently occurred in norovirus outbreaks caused by GII.4 and those in healthcare settings. These results should help guide preventive interventions for targeted populations, including vaccine development.

Keywords: gastroenteritis; norovirus; outbreaks.

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Conflict of interest statement

Conflict of Interest: All authors report no commercial or other association that might pose a conflict of interest

Figures

Figure 1.
Figure 1.
Transmission modes (A) and settings (B) of norovirus outbreaks reported to the National Outbreak Reporting System and CaliciNet, 2009–2016. * Chi-square p =0.18 for difference between GII.4 and non-GII.4 outbreaks with environmental transmission. For all other transmission modes and for all settings displayed, Chi-square p <0.001. # Other healthcare settings include: hospital, dialysis center, and “other healthcare facility.” + Other settings include: private residence, prison/jail, office, hotel/motel, religious facility, grocery store, ship/boat, “other.”
Figure 2.
Figure 2.
Multivariable analysis of characteristics associated with norovirus genotype GII.4 versus non-GII.4 genotypes in outbreaks reported to the National Outbreak Reporting System (NORS) and CaliciNet, 2009–2016
Figure 3.
Figure 3.
Rate ratios from multivariable analysis of characteristics associated with hospitalization (A) and mortality (B) from norovirus outbreaks reported to the National Outbreak Reporting System (NORS) and CaliciNet, 2009–2016
See this image and copyright information in PMC

Comment in

References

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