Abstract: Aim: Recent literature has shown epidemiological changes in bronchiolitis with an increased incidence in the post-SARS-CoV-2 pandemic period but reports regarding disease severity are conflicting. We aimed to describe the epidemiology, disease severity, and microbiology of bronchiolitis during the 2022-2023 cold season compared to the previous five years. Methods: This single-center retrospective observational study at IRCCS Gaslini, Italy, included all children aged 0-2 years hospitalized for bronchiolitis from September 1st, 2017, to August 31, 2023. Findings from the 2022-2023 season were compared to the previous five years. Results: We observed a statistically significant increase in the 2022-2023 season in the absolute number of bronchiolitis admissions. Children who required mechanical ventilation dramatically increased from a total of 7 patients in the previous five seasons to 17 in the 2022-2023 season alone ( p=0.001). All other severity parameters significantly increased: the need for respiratory support ( p=0.002) , the median length of stay (5 vs. 4, p=0.001), and the median duration of respiratory support (4 vs. 3, p=0.016). Conclusions: We report a substantial increase in the severity of bronchiolitis in the season 2022-2023 with a remarkable number of previously healthy infants requiring mechanical ventilation. Our data represents a call in our setting for urgent measures to plan prophylactic and therapeutic strategies and prepare healthcare systems. Further studies are needed to confirm whether our findings are an isolated phenomenon or part of a true global trend. Health systems need to be prepared and protective preventive measures should be implemented for all newborns.

Objective: SARS-COV-2 pandemic had a profound impact on acute bronchiolitis epidemiology, especially in RSV diffusion and the burden of disease with implications on the management of prophylaxis and health resources. We aimed to compare clinical and epidemiological characteristics of bronchiolitis before and during the SARS-CoV-2 pandemic.   Methods: We conducted an observational study involving children aged 0-2 years with bronchiolitis admitted to a tertiary children’s hospital during the last 5 years. Demographic, clinical, microbiological, and outcome data were collected. Comparison between pre- and post-pandemic period, RSV positive versus non-RSV patients, and SARS-CoV-2 positive vs negative patients were carried out.    Results: A total of 647 patients admitted for bronchiolitis were included (264 female,40.8%, median age 78 days). Molecular diagnostic tests were performed in 617 patients (95.4%) with RSV detected in 62.5% of patients. SARS-CoV-2 was found in 3.9% of hospitalized bronchiolitis (3.9%). We observed a progressive increase in bronchiolitis admissions and a statistically significant increase over the years in the need for respiratory support. Conversely, this was not true for mechanical ventilation, duration of respiratory support, ICU admission, and length of stay. During the pandemic period children with prematurity increased, although only 1 child had an indication for prophylaxis. Discussion: We confirm the stronger impact of bronchiolitis in the 2021-22 season, which is likely explained by the higher prevalence of RSV and the immunity debt theory. However, our findings were conflicting in terms of worsening clinical severity. The increase of children with prematurity and the inter-seasonal spread of RSV highlight the importance of epidemiological surveillance systems that monitor RSV circulation.

Necrotizing pneumonia and severe COVID-19 in an infant with CR-BSI by methicillin-susceptible Staphylococcus aureusGiacomo Brisca1, Silvia Buratti2, Daniela Pirlo1, Luca Basso3, Marta Romanengo1, Maurizio Miano4, Alessio Mesini5, Pietro Salvati6, Andrea Moscatelli1,2, Elio Castagnola5.Sub-Intensive Care Unit, IRCCS Istituto Giannina Gaslini, Genoa, ItalyNeonatal and Pediatric Intensive Care Unit, IRCCS Istituto Giannina Gaslini, Genoa, ItalyRadiology Unit, IRCCS Istituto Giannina Gaslini, Genoa, ItalyHematology Unit, IRCCS Istituto Giannina Gaslini, Genoa, ItalyInfectious Disease Unit, IRCCS IstitutoGianninaGaslini, Genoa, ItalyPneumology Unit, IRCCS Istituto Giannina Gaslini, Genoa, Italy