Variation in the seasonality of the respiratory syncytial virus during the COVID-19 pandemic

Background The COVID-19 pandemic has caused a variation in the circulation of common respiratory viruses. Our objective was to analyse the epidemiology of respiratory syncytial virus (RSV) bronchiolitis admissions during the COVID-19 pandemic in comparison with previous epidemic seasons. Methods We conducted an observational study involving infants with RSV bronchiolitis admitted to a tertiary hospital during two periods: pandemic COVID-19 (15 March 2020–30 September 2021) and pre-pandemic (1 October 2014–14 March 2020). Demographic and clinical characteristics were collected. Results A total of 270 patients were admitted for RSV bronchiolitis: 253 in the pre-pandemic period with an average of 42 admissions per season vs 17 in the pandemic. During the pandemic, the RSV outbreak started late in June 2021 with a higher percentage of prematurity and PICU admissions. Conclusion A change in RSV seasonality was observed during the COVID-19 pandemic, with an unusual outbreak in summer 2021 of lower magnitude than previous seasons.