Age-related clinical characteristics of respiratory syncytial virus infection in hospitalized children: a retrospective study.

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in children, yet age-stratified clinical characteristics of hospitalized children with RSV infection remain incompletely defined. This study aimed to compare the clinical manifestations, laboratory parameters, co-infections, and disease severity between hospitalized children with RSV infection aged ≤3 years and those aged >3 years, so as to provide evidence for age-stratified diagnosis, treatment, and prevention of RSV infection.

METHODS

A total of 624 hospitalized children with RSV infection admitted to Beijing Friendship Hospital, Capital Medical University, from 2023 to 2025 were retrospectively enrolled. Based on age at admission, patients were stratified into two groups: ≤3 years (n=434) and >3 years (n=190). Demographic characteristics, clinical manifestations, laboratory parameters, etiological findings, and treatment data were collected. Intergroup comparisons were performed using the χ2 test, Fisher's exact test, Mann-Whitney U test, or independent samples t-test, as appropriate.

RESULTS

Compared with the ≤3 years group, the >3 years group had higher rates of fever (92.6% vs. 79.5%), longer fever duration (6 vs. 5 days), severe pneumonia (13.7% vs. 6.7%), co-infection (47.4% vs. 26.0%), and longer disease course (10 vs. 8 days) (all P<0.001, except severe pneumonia P=0.005). Co-infection with Mycoplasma pneumoniae (33.7% vs. 10.1%) and other viruses (20.0% vs. 12.7%) was also more frequent in the >3 years group (all P<0.05). The ≤3 years group showed higher wheezing rates (22.6% vs. 6.3%, P<0.001). Laboratory findings revealed higher neutrophil counts (3.16×109/L vs. 2.44×109/L) and C-reactive protein (CRP) levels (3.5 vs. 1.3 mg/L) but lower white blood cell (WBC) count and lymphocyte counts in the >3 years group (all P<0.001). Glucocorticoid (11.6% vs. 7.8%) and intravenous immunoglobulin (IVIG) use (1.1% vs. 1.2%) were comparable between groups (P>0.05).

CONCLUSIONS

Compared with children aged ≤3 years, hospitalized children aged >3 years with RSV infection had higher proportions of fever, prolonged disease course, co-infection, and severe pneumonia. Early recognition and dynamic assessment should be emphasized in this age group to avoid underestimating disease severity based on age alone.