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J Infect Dis. 2018 Nov 15. doi: 10.1093/infdis/jiy569. [Epub ahead of print]

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

Author information

1
Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Atlanta, Georgia.
2
Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, Georgia.
3
IHRC, Inc, Atlanta, Georgia.
4
Oak Ridge Institute for Science and Education, Tennessee, Atlanta, Georgia.
5
CDC Foundation, Atlanta, Georgia.

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.

PMID:
30445538
DOI:
10.1093/infdis/jiy569

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