Etiological analysis of acute respiratory infections in hospitalized children after the relaxation of COVID-19 non-pharmacological interventions in Quzhou, China

Abstract Background: Acute respiratory infections (ARIs) can cause morbidity and mortality in children. This study was to determine the characteristics of pathogens in hospitalized children with ARIs after the relaxation of COVID-19 non-pharmacological interventions (NPIs) in Quzhou, China. Methods: Hospitalized children with ARIs were enrolled between May and October 2023, and thirteen common respiratory pathogens were tested by fluorescent quantitative polymerase chain reaction. Mono- and co-infections were assessed, and the association between pathogens and age was explored using restricted cubic spline analysis. Results: A total of 1225 children were included, 820 of them detected one pathogen and 238 of them detected two or more pathogens. Children aged 1-3 years had the highest positive detection rates. The dominant pathogen varied monthly. Mycoplasma pneumoniae (Mp) was the most common pathogen in monoinfection, followed by respiratory syncytial virus (RSV) and human rhinovirus (HRV), while influenza virus was detected at a lower rate. Mp+HRV was the most common combination of coinfections. The detection rates of Mp and HRV were higher in coinfections than in monoinfection, but there was no difference in the detection rate of RSV. In the restricted cubic spline models, a J-shaped association was consistently observed between age and Mp infection, the risk of HRV first increased and then decreased, the risk of RSV was relatively flat until 1.5 years and then decreased raplidly. Conclusion: Our study revealed the epidemiological characteristics of ARIs pathogens after the relaxation of NPIs. There is still a need to enhanced pathogen surveillance, especially for Mp.