Spatiotemporal trends, evolving seasonality and symptoms of dengue in Bangladesh, 2019-2025

Background Bangladesh has experienced an unprecedented increase in dengue incidence since 2019, with altered transmission patterns indicating changes in geographic spread, seasonality, and disease severity. We aimed to investigate ongoing trends in epidemiology, seasonality, and changes in disease prognosis from 2000 to 2025. Methods We screened and analyzed data from the national dengue surveillance system (2000–2025) and environmental factors from the World Bank Climate Portal and national meteorological databases. We compared prevalence, incidence, rural to urban distribution, disease prognosis and seasonality between 2000–2018 and 2019–2025. Results Dengue transmission in rural and semi-urban regions increased sharply from 2019, with rural-to-urban incidence ratios increasing from 0.11–0.41 (2000–2018) to 0.86–2.12 (2019–2025). SIRs declined in major hotspot cities despite significant increase of nationwide cases. After 2019, the seasonal peak shifted toward October–November, with significantly higher incidence ( p 0.5). Available surveillance records indicated rapid clinical deterioration within 24–72 hours following diagnosis among a subset of fatal cases. Conclusion Our study suggests possible changes in epidemiologic and clinical trends of dengue and underscores the need for continuous vector surveillance, integrated virological and serological studies to address the emerging risks and predict the interventions.