COVID-19 pandemic reshaped seasonal patterns and age distributions of respiratory viruses

Summary Objectives This study aims to investigate the changes in the prevalence and demographic characteristics of common respiratory viruses during and after the COVID-19 pandemic. Methods We retrospectively enrolled children with acute respiratory infections (ARIs) at Shiyan Renmin Hospital, Hubei University of Medicine, from January 2020 to December 2023. Specimens serum, nasopharyngeal aspirate, and alveolar lavage fluid were collected for direct immunofluorescence assay (DFA): respiratory syncytial virus (RSV), adenovirus (ADV), influenza A virus (IAV), influenza B virus (IBV), and parainfluenza virus (PIV). Demographic data and laboratory test results were analyzed accordingly. Results A total of 10,193 patients were enrolled. The positive infection rates for the years 2020, 2021, 2022, and 2023 were 3.97%, 3.15%, 36.20%, and 38.82%, respectively. The seasonal patterns for ADV transitioned from peaking in the summer and autumn of 2022 to summer and winter in 2023, while RSV peaked in the spring and summer of 2022 but moved to spring and autumn in 2023. PIV shifted from autumn 2022 to both spring and autumn in 2023. Intriguingly, IAV stably remained a two-season pattern of summer and winter in 2022 and 2023, while IBV showed up at 2022 winter but largely diminished later. The age distribution of children infected with ADV, RSV and PIV showed an upward trend, while no significant changes were observed for IAV and IBV. Conclusions The COVID-19 pandemic has disrupted the seasonal circulation of respiratory viruses. The seasonal pattern of influenza virus has been restored in 2022. In contrast, ADV, PIV, and RSV showed significant seasonal changes after the pandemic. The increasing age distributions of cases indicates an expanded age range of infection. Continuous monitoring of pathogen distribution and adjustment of preventive strategies are crucial for the effective management of pediatric ARIs.