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.