Changing in epidemiology of respiratory syncytial virus infection among children younger than 5 years old during COVID-19 pandemic in northern Taiwan.

Abstract

Background: Respiratory syncytial virus (RSV) is a leading cause of respiratory infections in infants and young children. The COVID-19 pandemic significantly disrupted global RSV epidemiology. This study aimed to investigate the impact of the pandemic on RSV epidemiology in northern Taiwan from 2018 to 2023.

Methods: We retrospectively enrolled children aged <5 years with positive RSV antigen tests from 2018 to 2023, dividing into four study periods based on the COVID-19 pandemic timeline: 2018-2019, 2020-2021, 2022, 2023.

Results: The number of RSV positive cases was 1155 in 2018-2019, 780 in 2020-2021, 784 in 2022, and 1116 in 2023. The proportion of RSV-positive children aged 2-5 years increased progressively from 23.9 % (2018-2019) to 52.0 % (2023) (P < 0.001). The mean age of infected children increased over time (P < 0.001). Among children under 2 years old, hospitalization rates declined from 82.0 % (2018-2019) to 68.1 % (2023) in subsequent intervals (P < 0.001). Compared to 2018-2019, seasonal peaks delayed by 2 months in 2020, absent in 2021, and delayed by 3 and 2 months in 2022 and 2023, respectively. The RSV seasonal peaks varied with shortened peaks during the COVID pandemic. ICU admission rates declined from 2.9 % to 1.9 % while mortality declined from 0.2 % to 0 %. Independent risk factors for severe disease included age under 3 months, bronchopulmonary dysplasia, congenital heart disease, cerebral palsy, neurodevelopmental disorders, and co-infection with Streptococcus pneumoniae.

Conclusions: The COVID-19 pandemic significantly altered the seasonality and clinical characteristics of RSV infections in northern Taiwan, likely due to the varying intensity of public health interventions.