Characteristics of Respiratory Syncytial Virus infections in children in the Post-COVID seasons: a Northern Italy Hospital experience.

Background: Public health measures for COVID-19 mitigation influenced the circulation of Respiratory Syncytial Virus (RSV) during the 2020-2021 winter season. In the following autumn, an unprecedented resurgence of RSV occurred. In our study we monitored RSV pediatric infections, one and two years after the relaxation of containment measures for COVID-19 pandemics. Methods: we analyzed diagnostic molecular data for SARS-CoV-2, Flu and RSV infections and clinical data from children with respiratory symptoms referring to our hospital during 2021-2022 and 2022-2023 seasons. Results: In 2021-22 season, the number of RSV affected children was very high, especially for babies <1 year. The outbreak appeared in a shorter interval of time, with a high clinical severity. In the 2022-23 season, a reduced number of infected pediatric patients were detected, with a similar hospitalization rate (46% vs 40%) and RSV accounted for 12% of the infections. Coinfections were observed in age <2 years. In RSV patients, symptoms were similar across the two seasons. Conclusions: clinical presentation of RSV in the two post-COVID seasons suggests that the pathophysiology of the virus did not change across these two years. Further studies are needed to continuously monitor RSV, for supporting an effective prevention strategy.