Epidemiology of Norovirus Outbreaks in Kindergartens, Primary Schools, and Junior High Schools in Xi\'an, China, From October 2020 to February 2023

BACKGROUND Norovirus outbreaks frequently occur in semi-closed environments like schools and kindergartens. Current strategies are inadequate. This study aimed to examine several important characteristics of norovirus outbreaks in kindergartens, primary schools, and junior high schools reported to the Xi'an Center for Disease Control and Prevention (CDC) between October 2020 and February 2023. MATERIAL AND METHODS Data were obtained from the Xi'an CDC. Attack rates, vomiting rates, diarrhea rates, norovirus detection rates, and asymptomatic prevalence among exposed populations were analyzed using a random-effects meta-analysis model. Between-group comparisons were made using the Wilcoxon signed-rank test and Kruskal-Wallis H test. RESULTS Forty-four norovirus outbreaks were analyzed, involving 33 kindergartens and 11 schools, with 7945 exposed individuals and 768 cases. The overall attack rate was 29.1% (95% confidence interval [CI]: 22.9-35.6). Vomiting was reported in 90.9% of the cases (95% CI: 84.6-95.9), whereas diarrhea occurred in 23.3% of the cases (95% CI: 15.8-31.5). Norovirus was detected in 65.6% of the cases (95% CI: 57.6-73.2) using PCR-based methods. Additionally, the asymptomatic prevalence during the outbreaks was 17.4% (95% CI: 9.7-26.3). CONCLUSIONS These findings reveal the impact of norovirus on student populations in schools and kindergartens. Understanding the epidemiological characteristics of norovirus outbreaks enables the prompt identification of norovirus as a potential causative agent in an acute gastroenteritis outbreak. This facilitates the timely implementation of control measures, limits the spread and scale of these outbreaks, shortens their duration, guides the efficient allocation of medical resources, and reduces unnecessary resource consumption.