Epidemiological characteristics of respiratory syncytial virus infection in pediatric patients before, during the COVID-19 pandemic and after easing of COVID-19 restrictive measures in China.

We aimed to assess the epidemiological characteristics of respiratory syncytial virus (RSV) infection in Chinese children at different phases of the coronavirus disease 2019 (COVID-19) pandemic, that is, before, during the pandemic and after easing of restrictive measures. We included 123 623 patients aged 0-18 years with respiratory infection symptoms who were suspected with RSV infection from January 1, 2019 to June 30, 2023 in Hangzhou Children's Hospital. Clinical information and RSV test result were extracted from the laboratory information system. We calculated the positive rate of RSV detection by age groups, gender, seasons, types of patients and phases of COVID-19 pandemic. Nonlinear associations between age and risk of RSV infection in three phases of pandemic were assessed by restricted cubic spline regression models. Among 123 623 patients, 3875 (3.13%) were tested as positive. The highest positive rate was observed in children aged 0-28 days (i.e., 12.28%). RSV infection was most prevalent in winter (6.04%), and followed by autumn (2.52%). Although there is no statistical significance regarding the positive rate at three phases of the pandemic, we observed that the rate was lowest during the pandemic and increased after easing the measures in certain age groups (p < 0.05), which was consisted with results from the nonlinear regression analyses. In addition, regression analyses suggested that the age range of children susceptible to RSV got wider, that is, 0-3.5 years, after easing all restrictive measures compared with that before (i.e., 0-3 years) and during the pandemic (i.e., 0-1 year). Based on our findings, we called for attention from health professionals and caregivers on the new epidemiological characteristics of RSV infection in the post-pandemic era after easing the restrictive measures.