Delayed Seasonality but Consistent Age Burden: RSV Epidemiology Pre–, During, and Post–COVID-19 Pandemic on the Kenyan Coast (2008–2026)
Abstract
Abstract Background The COVID-19 pandemic and associated nonpharmaceutical interventions disrupted the established epidemiological patterns of many endemic respiratory viruses globally. However, its impact on respiratory syncytial virus (RSV) epidemiology in sub-Saharan Africa is understudied. Methods We analyzed data from a continuous hospital-based pediatric pneumonia surveillance program in coastal Kenya January 2008–June 2026. Children ≤5 years, admitted with World Health Organization–defined syndromic severe or very severe pneumonia were tested for RSV using quantitative reverse transcriptase polymerase chain reaction. The period was stratified into prepandemic (January 2008–March 2020), during pandemic (March 2020–May 2023), and postpandemic (May 2023–June 2026). Multivariable logistic regression evaluated clinical and demographic shifts across periods. Results Among 10 374 tested children, 2442 (23.5%) were RSV positive. Positivity declined from 25.3% (1919/7585) prepandemic to 18.3% (235/1282) during the pandemic and 19.1% (288/1507) postpandemic. Overall median age of RSV-positive patients remained statistically consistent across all periods (4.3 vs 3.7 vs 3.1 months; P = .108), with ≤6-month-olds accounting for ∼62% of admissions throughout. However, in the 2020–2021 season, RSV-positive children had increased median age (6.7; interquartile range: 2.0–15.1 months). In multivariable analysis, fever was less frequent during and postpandemic (adjusted P < .001), and cough decreased postpandemic (adjusted P = .002). Pneumonia severity and overall mortality did not significantly differ across the periods. Local RSV season onsets exhibited 1–2 months’ delay during and postpandemic compared to prepandemic. Conclusions Despite a repeated 1- to 2-month delay of RSV season onsets on the Kenyan coast and minor clinical symptoms shifts, the core demographic patterns remained stable. The persisting severe RSV disease in <6-month-olds highlights this population for RSV interventions.