New epidemiological trends of respiratory syncytial virus bronchiolitis during COVID-19 pandemic

Restrictive measures adopted worldwide against COVID 19 (e.g., wearing masks, frequent hand washing, and social distancing) produced not only a decrease in SARS-CoV-2 difusion but also a drastic reduction in respiratory diseases caused by other pathogens, as reported by many authors. The spread of respiratory viruses, particularly respiratory syncytial virus (RSV), has been completely changed during the winter of 2020–2021, but an unusual resurgence of RSV infection has been recently reported in diferent countries. A drastic reduction in bronchiolitis hospitalizations also occurred during the winter of 2020–2021, with RSV being the main etiologic agent of bronchiolitis. We described the unusual RSV bronchiolitis outbreak in young infants in autumn 2021 and the diference in RSV bronchiolitis epidemiology during the COVID-19 pandemic season (March 2020–September 2021) compared to previous seasons. We retrospectively analyzed all infants aged <6 months with acute bronchiolitis admitted to the Pediatric Emergency Department (PED) of our tertiary teaching children’s hospital from October to November 2021 compared to those admitted during the same period from 2017 to 2020.