Background:
Respiratory syncytial virus (RSV) is the main cause of hospitalization for acute respiratory infection (ARI; WHO case definition) in children under 5 years and the third viral cause of hospital admission in over 65. The main objective of this study is to evaluate the burden of RSV-related disease in the primary care setting, to support future prevention strategies. Secondary objectives are 1) to describe the epidemiological trend of ARIs, 2) to identify the predictive parameters of the clinical presentation severity, complications, socio-economic and healthcare impact.

Methods:
As part of the RSVComNet project, in 2019/20 and 2021/22 winter seasons, in Lazio, Puglia, Liguria and Lombardia regions (representing 40% of the Italian population), children under 5 years with ARI were enrolled and subjected to a nasopharyngeal swab for the differential diagnosis of the main respiratory infectious agents. Parents of RSV-positive children completed a 14-day and 30-day follow-up questionnaire. In 2022/23, Tuscany will also participate in the study, also enrolling adults over 65.

Results:
In 2019/20 and 2021/22, 493 children were diagnosed with ARI and 187 (37.9%) were positive for RSV. The median disease duration was 9.5 days (IQR 7-14), with a median of 1 extra visit by their pediatrician (IQR: 1-2). 12 children (6.6%) were hospitalized (10