Long-Term Dynamics of Pediatric Respiratory Pathogens Before, During, and After the COVID-19 Pandemic: Evidence From Nine Years of Surveillance in the Netherlands (2015–2023)

Respiratory tract infections (RTIs) are common in children and are caused by viral and bacterial pathogens. However, seasonal variability and limited age-specific data obscure a clear understanding of their epidemiology and clinical outcomes. The annual incidence of respiratory pathogens, co-infections, and disease burden was retrospectively investigated. Clinical data and respiratory swabs were collected from children < 18 years who presented with respiratory symptoms at a Dutch Emergency Room between 2015 and 2023. Swabs were tested for 20 common pathogens using MLPA technology. In total, 3575 samples were collected from 2969 children. 74% of swabs were positive for at least one pathogen. Rhinovirus (RV: 36.8%), respiratory syncytial virus (RSV: 19.5%), and adenovirus (5.3%) were detected most often. Pathogen co-detections occurred in 20.8% of all positive samples, with the combination RV-bocavirus (3.6%) being the most common. In < 12-month-olds, the need for hospitalization was associated with RV (84%), RSV (84%), or influenza (80%). After adjusting for covariates, the need for respiratory support was associated with infections caused by human metapneumovirus and RSV. Interestingly, Mycoplasma pneumoniae was circulating year-round and almost exclusively identified in children over 2 years of age, of whom most required hospitalization (81%), respiratory support (60%), and antibiotics (89%). Longitudinal data collected over nearly a decade provided insights into the seasonality and burden of respiratory pathogens in children. RSV burden remains high, especially in infants < 6 months, whereas M. pneumoniae infections are common, especially in children > 2 years. These results may inform current diagnostic guidelines and suggest age-specific adaptations and monitoring.