RSV seasonality in hospitalized Malaysian children rebounded after pandemic disruption

Respiratory syncytial virus (RSV) showed distinct seasonal peaks among hospitalized children in Negeri Sembilan, Malaysia, that were disrupted during the COVID-19 pandemic years and re-established in 2024, according to an eight-year analysis of laboratory surveillance data. The study, conducted by researchers from Malaysia’s Institute for Medical Research, Hospital Tuanku Ja’afar Seremban and other Ministry of Health institutions, examined weekly RSV detections among children under 12 years old admitted with acute lower respiratory tract infections between epidemiological week 1 of 2017 and week 52 of 2024, spanning 417 continuous weeks.

Across the study period, 6,545 of 45,817 tested samples were positive for RSV, a positivity rate of 14.29 percent. Before the pandemic, cases historically peaked between July and September.

To disentangle the drivers of RSV transmission, the team used time-series decomposition and autocorrelation functions to characterize seasonality, then applied an autoregressive integrated moving average model with exogenous variables, ARIMAX (2,0,4)(1,0,0)52, to test the influence of co-circulating viruses, meteorological conditions and public holidays. The modeling indicated that RSV dynamics were driven primarily by internal autoregressive patterns, meaning recent levels of RSV activity themselves were the strongest predictor of subsequent cases, rather than by meteorological factors.

Two exogenous factors did show statistically significant associations. Major public holidays had a dual effect: reported cases decreased immediately during the holiday period (p = 0.012) and then surged afterward (p = 0.014). The authors interpret this pattern as consistent with changes in social mixing, with reduced contact during holidays followed by increased transmission when gatherings and travel resume. Because these are modeled associations from observational surveillance data, they do not establish causation directly.

Influenza activity was also a significant predictor of RSV cases with a one-week lag (p = 0.012). This finding is consistent with the hypothesis of viral interference, in which infection with one respiratory virus may temporarily modulate susceptibility to or transmission of another, although the observational design cannot confirm a causal mechanism.

The study’s setting matters for interpretation. Unlike temperate regions with pronounced winter RSV seasons, tropical settings such as Malaysia experience RSV year-round with seasonal fluctuations, making locally derived timing data especially relevant for immunization planning.

The analysis has limitations inherent to its design. It covers a single Malaysian state and relies on hospitalized pediatric patients with lower respiratory tract infections, so the findings may not generalize to community cases, outpatient illness or other regions. The ARIMAX framework captures statistical associations and lagged relationships, not proven biological mechanisms.

For public health planners, the practical signals are the restored July-to-September peak, the predictable post-holiday surge in cases, and the potential value of monitoring influenza activity as an early indicator for RSV waves.

Subject of Research: Seasonality and drivers of RSV infections among hospitalized children in Negeri Sembilan, Malaysia, from 2017 to 2024

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

Article References: Iderus, N. H. M., Singh, S., Ng, D. C.-E., Ghazali, S. M., Ghazali, N. M., Lim, M. C., Ahmad, N. A. R., Ruslan, Q., Liew, C.-H., Ali, M. M., Abidin, N. Z. Z., Yusoff, N. H. M., Gill, B. S., Omar, M. A., & Ahmad, L. C. R. Q. (2026). Epidemiology and seasonality of respiratory syncytial virus among hospitalized pediatric patients with lower respiratory tract infections in Negeri Sembilan, Malaysia (2017–2024). Frontiers in Public Health, 14, Article 1947126. https://doi.org/10.3389/fpubh.2026.1947126

Image Credits: AI Generated

DOI: 10.3389/fpubh.2026.1947126

Keywords: RSV, respiratory syncytial virus, seasonality, Malaysia, pediatrics, lower respiratory tract infection, ARIMAX, time series, influenza, public holidays, surveillance, pandemic disruption