Frontiers in Public Health · Published 2026-08-03 · DOI 10.3389/fpubh.2026.1892098
Jaime Angamarca-Iguago, Jaen Cagua-Ordóñez, Juan Marcos Parise-Vasco, Doménica de Mora, Mónica Escobar-Naranjo, Alfredo Bruno, Daniel Simancas-Racines
BackgroundAcute bronchiolitis, mainly attributed to respiratory syncytial virus (RSV), is the leading cause of infant hospitalization for lower respiratory tract disease worldwide. Nirsevimab and maternal RSVpreF (Abrysvo) confer about 6 months of protection, so timing relative to the season affects their impact. Ecuador spans the equator from sea level to valleys above 4,000 m and is considering introducing these products, yet lacks subnational evidence on the seasonality of bronchiolitis, altitudinal patterning, or post-pandemic stability.MethodsWe conducted a national ecological time-series analysis of hospital discharges from the Ecuadorian Statistics Institute, 2007–2024 (19,788,097 discharges; 204 of 224 cantons had complete data and formed the analytic panel). The primary outcome was acute bronchiolitis (ICD-10 code J21) in children younger than 12 months (n = 23,190 nationally; 22,724 in the panel), with secondary outcomes across three RSV-relevant age bands, ICD-10 code J21 under 5 years, and two RSV-specific ICD-10 codes (J12.1 and J20.5; 2018–2024). K35 (appendicitis) was a negative control. Analyses combined circular seasonality metrics with block-bootstrap confidence intervals (CIs), year-by-year disaggregation, and complementary sensitivity analyses [Moving Epidemics Method (MEM), Bai–Perron breaks, and lagged climate correlations].ResultsThe weighted circular peak month of infant bronchiolitis hospitalizations shifted after the pandemic in Costa (+2.16 months), Sierra (+1.22), and Amazonía (+1.91), attenuating with altitude from +2.19 months below 500 m to +0.88 at 1,500–3,000 m. Costa was stable across 2022–2024; Sierra and, more so, Amazonía varied widely year to year (Amazonía peak ranged March–July, n = 37–42/year), so the pooled estimate should be read with caution. The composite RSV-coded outcome tracked ICD-10 code J21's timing closely in Costa (0.15-month difference) and Sierra (0.40), supporting ICD-10 code J21 as a reasonable RSV proxy in both, and the three regional peaks now span 2 months.ConclusionBronchiolitis seasonality in Ecuador changed after the pandemic, most clearly and stably in Costa; Sierra showed a transient 2022 perturbation with partial reversion by 2023–2024, and Amazonía's estimates remained unstable and underpowered. As region-tailored estimates are less stable in Sierra and Amazonía than in Costa, a single national window (nirsevimab February–April; maternal RSVpreF for pregnancies expected to deliver January–May) is a more defensible starting point, pending confirmation from further seasons and, ideally, laboratory-confirmed surveillance.
Abstract from DOAJ. Public domain (CC0 1.0).
Read the article at the publisher →
Angamarca-Iguago, J., Cagua-Ordóñez, J., Parise-Vasco, J., et al. (2026). Regional, altitudinal, and age-specific heterogeneity of bronchiolitis hospitalization seasonality in Ecuador, 2007–2024, and implications for RSV immunoprophylaxis timing. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2026.1892098