Clinical characteristics and risk factors for severe community-acquired pneumonia in hospitalized children with human metapneumovirus infection in Shanghai: a retrospective cohort study

Background HMPV is a leading cause of pediatric lower respiratory tract infections, second only to respiratory syncytial virus in causing severe pneumonia in children. Its clinical presentation closely mimics other common respiratory viruses, making diagnosis challenging. This study aimed to characterize the clinical profile and identify independent risk factors for severe community-acquired pneumonia (CAP) in hospitalized children with human metapneumovirus (HMPV) infection. Methods We conducted a retrospective cohort study of 878 children hospitalized with HMPV-positive CAP at Shanghai Children’s Hospital from 2021 to 2024. Patients were classified into mild ( n = 632) and severe ( n = 246) groups based on established CAP criteria. Data on demographics, clinical features, laboratory findings, and concomitant pathogen detection were collected. Multivariate logistic regression was used to identify independent risk factors for severe disease. Results The severe group comprised 28.0% of the cohort. Key clinical manifestations included fever (98.0%), cough (97.6%), wheezing (56.5%), and pulmonary crackles (84.6%). Compared to the mild group, the severe group had significantly higher rates of premature birth, wheezing, elevated inflammatory markers (NLR > 1, PCT > 1 ng/mL, CRP ≥ 50 mg/L), and co-infection with Mycoplasma pneumoniae (MP) (all P < 0.05). Multivariate analysis identified premature birth (odds ratio [OR] = 2.43, 95% CI: 1.45–4.07), wheezing (OR = 3.47, 95% CI: 2.51–4.80), NLR > 1 (OR = 1.75, 95% CI: 1.26–2.43), PCT > 1 ng/mL (OR = 2.38, 95% CI: 1.42–3.99), CRP ≥ 50 mg/L (OR = 2.20, 95% CI: 1.19–4.06), and co-infection with MP (OR = 2.17, 95% CI: 1.53–3.08) as independent risk factors for severe CAP in children with HMPV infection. Conclusion Approximately 28% of hospitalized children with HMPV-positive CAP progress to severe disease. Premature birth, wheezing, elevated inflammatory markers, and co-infection with MP are independent risk factors, which can facilitate early risk stratification and targeted clinical management.