Significant reduction in norovirus outbreaks and secondary transmission of acute gastroenteritis in Seoul schools following the COVID-19 pandemic: a retrospective epidemiological study

BackgroundUnexpectedly, during the coronavirus disease 2019 (COVID-19) pandemic (2020–2022), it was reported that the number of acute gastroenteritis outbreaks (AGEOs) increased abruptly in childcare centers and kindergartens due to the increase in norovirus GII.4 transmission. However, changes in AGEOs in schools have not been reported during the same period. Therefore, this study aimed to compare the characteristics of AGEOs in schools before and after 2020. MethodsWe analyzed the results of AGEO epidemiological investigation reports in Seoul. ResultsThe number of AGEO cases in schools decreased after 2020. Norovirus was identified as the causative pathogen in 10 of 11 cases in 2019, while only five cases were caused by norovirus among the 12 cases between 2020 and 2022. The average attack rate decreased from 10.2% in 2019 to 5.2% between 2020 and 2022. The average duration of patient occurrence also decreased from 7.5 days in 2019 to 4 days between 2020 and 2022. Secondary transmission occurred in all 2019 cases. However, secondary transmission was not observed in half of the cases between 2020 and 2022. ConclusionNorovirus outbreaks and secondary transmission in schools declined after the onset of the COVID-19 pandemic, probably because of infection control measures implemented to prevent COVID-19 transmission.