Assessment of Respiratory Syncytial Virus infection in adults before, during and after the COVID-19 pandemic

Abstract

Background: Respiratory Syncytial Virus (RSV) is a leading cause of respiratory infec-tions and responsible for plenteous morbimortality across all age groups. While often associated with infants and young children, RSV infections can also have significant implications in older adults and those with underlying health conditions. The aim of this cross-sectional study is to evaluate the seasonality and prevalence of RSV before, during and after the COVID-19 pandemic in adults, in a tertiary care hospital in Portugal. Methods: From January 2018 to July 2024, samples from the respiratory tract were col-lected from adults with respiratory symptoms in the Emergency Department (ED) and Hospital Wards and tested for RSV by real-time reverse transcriptase PCR. Results: Before the COVID-19 pandemic RSV screening among adults was not a priority. During the pandemic, due to large-scale non-pharmaceutical interventions measures, no RSV infections were reported. After the relaxation of pandemic control measures, there has been an out-of-season increase. This pattern was observed in 2022 and 2023 and only restored to typical pre-pandemic season in 2024. The most affected were adults higher than 80 years old. This study shows a disruption of the seasonal RSV pattern and the efficacy of transmission mitigating measures among the adult population.