Viral spectrum differences between outpatients and inpatients with suspected pediatric acute respiratory infections: a prospective sentinel surveillance study in Pudong, Shanghai, China

BACKGROUND: Acute respiratory infections (ARIs) remain a leading cause of pediatric morbidity worldwide. However, comparative data on the viral spectra driving these infections across outpatient and inpatient settings within integrated unified health systems remain limited, especially in the post-COVID-19 era. METHODS: We conducted a prospective sentinel surveillance study in Pudong New Area, Shanghai (April 2023-March 2025), enrolling children under 15 years who presented with ARIs from both outpatient and inpatient settings. Nasopharyngeal swabs and clinical data were collected, and nine respiratory viruses were detected using a high-throughput microfluidic real-time polymerase chain reaction platform. RESULTS: Significant differences were observed among the 3,533 enrolled children (2,378 outpatients and 1,155 inpatients). Inpatients included a higher proportion of infants (0-2 years; 9.84% vs. 15.06%, P < 0.001), whereas adolescents (12-14 years) were more common among outpatients (14.47% vs. 6.75%, P < 0.001). Clinically, cough and expectoration were more frequent in inpatients, whereas runny nose and sore throat predominated in outpatients (P < 0.001). The overall viral detection rate was significantly higher in outpatients (34.36% vs. 19.91%, P < 0.001). Influenza virus (13.04% vs. 2.51%, P < 0.001) and severe acute respiratory syndrome coronavirus 2 (3.32% vs. 0.78%, P < 0.001) were predominant in outpatients, whereas respiratory syncytial virus (2.23% vs. 3.98%, P < 0.001) was significantly associated with hospitalization. Notably, RSV-B was dominant in outpatients (64.15%) compared to RSV-A in inpatients (58.70%, P = 0.020). Divergent seasonal circulation patterns were also identified. CONCLUSIONS: This study demonstrates that pediatric ARIs in outpatient and inpatient settings represent distinct epidemiological entities with fundamental differences in viral etiology, clinical presentation, and seasonality. These findings advocate the establishment of specific public health strategies to optimize resource allocation in tiered healthcare systems. CLINICAL TRIAL NUMBER: Not applicable.