Ambient PM₂.₅ exposure and increased dengue case fatality: a global multi-country analysis

Dengue is a rapidly expanding, climate- and environment-sensitive vector-borne disease. However, the role of air pollution in shaping its severity remains poorly understood. We aimed to assess whether long-term exposure to ambient fine particulate matter (PM₂.₅) contributes to increased dengue case fatality rates (CFRs) across endemic countries. We conducted a multi-country ecological study across 20 dengue-endemic nations in Asia, Africa, and Latin America during the period 2020-2024. National dengue surveillance data were integrated with satellite-derived PM₂.₅ estimates and socioeconomic-climatic covariates. Associations between long-term PM₂.₅ exposure and dengue CFRs were examined using generalized linear mixed-effects models. Results revealed that the mean dengue CFR across study countries was 0.20 % (range 0.05-0.77), with an annual mean PM₂.₅ exposure of 27.3 μg/m³ (range 7.4-77.5 μg/m³). However, countries exceeding 35 μg/m³ PM₂.₅ (e.g., Bangladesh, Burkina Faso, Indonesia) recorded 3-5 times higher CFRs than countries below 15 μg/m³ (e.g., Brazil, Ecuador, Costa Rica) (p < 0.001). Adjusted models identified PM₂.₅ concentration as an independent predictor of dengue mortality (IRR 1.94; 95 % CI 1.60-2.37). Each unit increase in PM₂.₅ concentration was associated with a 94 % higher risk of death, while higher GDP per capita was protective (IRR 0.65; 95 % CI 0.55-0.78). Seasonal analysis in Bangladesh revealed that dry-season PM₂.₅ (approximately 125 μg/m³) was associated with nearly doubled CFRs (0.82 %) compared to rainy seasons (0.45 %) when PM₂.₅ concentration is less than 50 μg/m³. By contrast, Brazil showed minimal seasonal variability in both air quality and dengue fatality. This study provides the first multi-continental evidence that exposure to higher ambient PM₂.₅ concentration is associated with increased dengue mortality. The convergence of high PM₂.₅ exposure and low GDP underscore global environmental injustice. Integrating air quality interventions into dengue control policies could yield critical co-benefits for both infectious disease prevention and environmental health.