Epidemic Pattern Changes in Influenza A and B and Mycoplasma pneumoniae Pediatric Respiratory Infections During and After the COVID-19 Pandemic Restrictions in Northwest China.

The COVID-19 pandemic significantly changed respiratory pathogen patterns in children. In this study, we aimed to provide evidence that may help guide prevention and control of pediatric respiratory diseases in the post-pandemic era. Thus, we conducted a retrospective study of children with respiratory symptoms who visited our hospital from January 2020 to December 2024. A total of 169,757 were tested for influenza A (IAV) and B (IBV) antigens, and 412,015 for Mycoplasma pneumoniae (MP) IgM antibodies. Demographic and laboratory data were extracted from electronic medical records and analyzed. We found that from 2020 to 2024, 16,042 children tested positive for IAV, 3,728 for IBV, and 82,760 for MP. Positivity rates varied significantly by year (P < 0.001). During the pandemic, detection rates for IAV, IBV, and MP remained low. After restrictions were lifted, IAV peaked in March 2023 and MP in November 2023. Detection rates for all three pathogens varied significantly by age (P < 0.001) and season (P < 0.001), both during and after the restrictions. Post-restriction age and seasonal patterns for IAV and MP were similar to those during the pandemic, while IBV showed minor shifts. Overall, following relaxation of pandemic measures, influenza viruses and MP resumed epidemic circulation in children. These findings highlight the importance of monitoring respiratory pathogen epidemiology to guide prevention and control in the post-pandemic era.