Epidemiology and seasonality of respiratory syncytial virus among hospitalized pediatric patients with lower respiratory tract infections in Negeri Sembilan, Malaysia (2017–2024)

Background Respiratory Syncytial Virus (RSV) remains a significant public health concern globally, with distinct seasonal patterns in temperate regions, while tropical settings experience RSV year-round with seasonal fluctuations. This study investigated seasonality and exogenous factors influencing RSV cases among hospitalized children under 12 years in Negeri Sembilan, Malaysia. Methods Weekly laboratory-confirmed RSV-positive cases among hospitalized pediatric patients presenting with acute lower respiratory tract infections (LRTIs) across 417 continuous WHO epidemiological weeks (EpiWeek 1, 2017 to EpiWeek 52, 2024) were analyzed using decomposition and autocorrelation functions. Relationships between RSV and co-circulating viruses, meteorological variables, and holidays were assessed via cross-correlation and Autoregressive Integrated Moving Average with Exogenous variables (ARIMAX) modeling. Results A total of 6,545 (14.29%) samples were RSV-positive from a total of 45,817 tested. Historical peaks (July–September) were disrupted during 2020–2023 but re-established in 2024. The ARIMAX (2,0,4) (1,0,0) 52 model revealed that RSV dynamics were driven primarily by internal autoregressive patterns rather than meteorological factors. Major public holidays exhibited a significant dual effect, with an immediate decrease in reported cases ( p = 0.012) followed by a significant surge ( p = 0.014). Influenza activity was a significant predictor with a one-week lag ( p = 0.012). Conclusion The pandemic temporarily shifted RSV seasonality, which has since normalized. The associations with holiday periods and influenza activity suggests that behavioral factors and viral interference may influence RSV circulation. These findings emphasize the need for dynamic surveillance to optimize the timing of future RSV immunizations in Malaysia.