Abstract
BACKGROUND: In the Democratic Republic of Congo (DRC), the influenza sentinel surveillance network established in 2007 has primarily focused on influenza and, more recently, COVID-19. However, limited data are available on the epidemiology of respiratory syncytial virus (RSV), one of the leading causes of lower respiratory infections in young children globally. This study aimed to describe RSV positivity rates, seasonal patterns, molecular subtypes, and sociodemographic correlates among children under five years of age. METHODS: We conducted a prospective cross-sectional analysis using data from the Influenza Sentinel Surveillance System (ISSS) collected between 2022 and 2023. Children under five years presenting with acute respiratory infections were enrolled at six sentinel sites in Kinshasa and Matadi. Oropharyngeal and nasopharyngeal swabs were collected and transported in viral transport medium to the National Institute of Biomedical Research (INRB) for molecular detection of RSV by real-time RT-PCR, followed by subtyping into RSV-A and RSV-B. Data were analysed using R software (version 4.0.4). Univariable and multivariable logistic regression models were used to assess associations between RSV infection and sociodemographic factors (age, sex, site, and year), with site included as a fixed effect. RESULTS: A total of 1,468 samples were analysed, of which 20.9% tested positive for RSV. Overall, 772 (53%) participants were males, the median age of RSV-positive children was 12 months (IQR: 18). Over the study period, RSV-B accounted for 52% of cases, predominantly affecting infants under nine months of age. RSV circulation exhibited a clear seasonal trend, with cases increased during the rainy season. We also noted a clear alternation between RSV-A and RSV-B subtypes across the two years. In the multivariable model, gender and year of data collection were significantly associated with RSV positivity: males were less likely to be infected than females (aOR = 0.76, 95% CI: 0.59–0.98, p = 0.036), and samples collected in 2023 had reduced odds of RSV infection compared with those from 2022 (aOR = 0.70, 95% CI: 0.53–0.91, p = 0.007). CONCLUSION: RSV remains an important cause of acute respiratory infections among children under five in the DRC, with distinct seasonal variation and subtype alternation. Integrating systematic RSV testing into national surveillance and enhancing genomic monitoring will be essential to guide targeted prevention and support future vaccine introduction efforts. CLINICAL TRIAL NUMBER: Not applicable. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12879-025-12224-3.