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. 2022 Jun 10;74(11):1906-1913.
doi: 10.1093/cid/ciab771.

Enteric Illness Outbreaks Reported Through the National Outbreak Reporting System-United States, 2009-2019

Mary E Wikswo  1 , Virginia Roberts  2 , Zachary Marsh  2 , Karunya Manikonda  2 , Brigette Gleason  2 , Anita Kambhampati  1   3 , Claire Mattison  1   4 , Laura Calderwood  1   4 , Neha Balachandran  1   4 , Cristina Cardemil  1 , Aron J Hall  1
Affiliations

Enteric Illness Outbreaks Reported Through the National Outbreak Reporting System-United States, 2009-2019

Mary E Wikswo et al. Clin Infect Dis. .

Abstract

Background: The National Outbreak Reporting System (NORS) captures data on foodborne, waterborne, and enteric illness outbreaks in the United States. This study describes enteric illness outbreaks reported during 11 years of surveillance.

Methods: We extracted finalized reports from NORS for outbreaks occurring during 2009-2019. Outbreaks were included if caused by an enteric etiology or if any patients reported diarrhea, vomiting, bloody stools, or unspecified acute gastroenteritis.

Results: A total of 38 395 outbreaks met inclusion criteria, increasing from 1932 in 2009 to 3889 in 2019. Outbreaks were most commonly transmitted through person-to-person contact (n = 23 812; 62%) and contaminated food (n = 9234; 24%). Norovirus was the most commonly reported etiology, reported in 22 820 (59%) outbreaks, followed by Salmonella (n = 2449; 6%) and Shigella (n = 1171; 3%). Norovirus outbreaks were significantly larger, with a median of 22 illnesses per outbreak, than outbreaks caused by the other most common outbreak etiologies (P < .0001, all comparisons). Hospitalization rates were higher in outbreaks caused by Salmonella and Escherichia coli outbreaks (20.9% and 22.8%, respectively) than those caused by norovirus (2%). Case fatality rate was highest in E. coli outbreaks (0.5%) and lowest in Shigella and Campylobacter outbreaks (0.02%).

Conclusions: Norovirus caused the most outbreaks and outbreak-associated illness, hospitalizations, and deaths. However, persons in E. coli and Salmonella outbreaks were more likely to be hospitalized or die. Outbreak surveillance through NORS provides the relative contributions of each mode of transmission and etiology for reported enteric illness outbreaks, which can guide targeted interventions.

Keywords: Salmonella; enteric illness; norovirus; outbreaks; surveillance.

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Conflict of interest statement

Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
National Outbreak Reporting System outbreak reports by year and mode of transmission, 2009–2019 (N = 38 395).
Figure 2.
Figure 2.
Rate* and number† of enteric illness outbreaks by state, 2009–2019 (N = 38 395). *Average annual incidence of outbreaks per state, per million population, on the basis of US Census Bureau population estimates, 2009–2019. †567 outbreaks in which exposure occurred in more than 1 state were assigned as an outbreak to each state involved. Abbreviations: DC, Washington, District of Columbia; PR, Puerto Rico.
Figure 3.
Figure 3.
Outbreak reports by month of first illness for selected confirmed or suspected etiologies, 2009–2019 (N = 35 214).
Figure 4.
Figure 4.
Symptoms reported by case-patients in outbreaks of selected confirmed or suspected etiologies, 2009–2019.
See this image and copyright information in PMC

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