The increase of bronchiolitis severity in the 2022-2023 season in an Italian tertiary children’s hospital: an isolated phenomenon or a warning sign?

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.