Epidemiology, temporal trends and co-infection of 13 respiratory pathogens in 32,125 children: a 3-year retrospective study.

Background: Pediatric acute respiratory tract infections bring heavy global disease burden. Clarifying post-pandemic epidemiological features guides clinical management and public health prevention. Methods: This retrospective study enrolled patients under 18 years receiving 13-pathogen multiplex PCR at West China Second University Hospital from 2023 to 2025. We extracted laboratory data and calculated pathogen positivity, single/co-infection proportions. Stratified analyses by year, season, age and sex and statistical collation of co-infection patterns were completed. Results: In total, 32,125 children were included. The total pathogen positive rate reached 63.4%, including 49.8% single infection and 13.6% co-infection dominated by dual infection. Human rhinovirus (22.9%) ranked first, followed by respiratory syncytial virus (15.2%). Pathogens varied obviously across seasons and ages: HRV surged in spring and autumn; parainfluenza, adenovirus and coronavirus prevailed in summer; syncytial virus and influenza peaked in winter. Respiratory syncytial virus mainly affected infants; rhinovirus and parainfluenza were prevalent in toddlers and preschoolers; Mycoplasma pneumoniae rose with age and peaked among school-age children. Dual infection occupied nearly all co-infections; the top non-influenza combinations were HRSV-HRV and HRV-HAdV. Infections with three or more pathogens were rare. Conclusions: HRV and HRSV dominated pediatric respiratory pathogens with obvious seasonal and age clustering. Most co-infections occurred in winter and young kids. HRV detection requires careful explanation for potential asymptomatic carriage. Local epidemiological characteristics should inform age-and seasonal-targeted diagnosis and targeted prevention including HRSV prevention.