ObjectiveTo investigate the etiology and epidemiological characteristics of pneumonia in children of different ages, to better characterize the co-infection patterns of pneumonia and their association with severe diseases. MethodsChildren aged 28 days to 13 years with pneumonia who were hospitalized in the Department of Pediatrics, Dongyang People's Hospital, Zhejiang Province from April 1 to December 28, 2023 were selected as the research subjects. Oropharynx swabs were collected from the patients within 24 hours of hospital admission, and PCR tests were conducted for 18 respiratory pathogens. Binary multivariate logistic regression analysis was used to analyze the status of viral and bacterial infection, patterns of co-infection in patients with different ages, and the risk factors for the outcome of severe pneumonia. ResultsA total of 2 191 hospitalized children with pneumonia were enrolled in the study. Severe cases were more common in children aged 5 years and older (53.3%) and in the second quarter of the year (46.5%). An average of (1.31±0.90) pathogens were detected in severe cases. Mycoplasma pneumoniae (44.4%, 973 cases) had the highest detection rate of pathogens. Streptococcus pneumoniae (21.7%, 476 cases) and rhinovirus (10.1%, 222 cases) were the most common bacteria and viruses, respectively, in hospitalized children with pneumonia in Dongyang City. Multivariate logistic regression analysis indicated positive interactions between different viral and bacterial pathogens. The adjusted OR (aOR) values for different respiratory pathogens in children with severe pneumonia varied significantly (all P<0.04). Among them, Chlamydia pneumoniae (aOR=9.74, 95%CI=2.36‒49.32, P<0.01), Mycoplasma pneumoniae (aOR=2.62, 95%CI=2.04‒3.37, P<0.01), and RSV (aOR=1.69, 95%CI=1.12‒2.54, P<0.01) were the risk factors for severe pneumonia. ConclusionIn the pathogen spectrum of children with pneumonia in Dongyang City, Zhejiang Province from April to December 2023, most viruses and bacteria exhibited positive interactions. Chlamydia pneumoniae, Mycoplasma pneumoniae, and RSV maybe the significant risk factors for severe pneumonia.