Highway paving dramatically increased dengue transmission in the Amazon

Human mobility drives the spread of many infectious diseases, yet the health impacts of mobility changes from new infrastructure development remain poorly understood and currently not accounted for in impact assessments. We present a novel application of a quasi-experimental approach to link mobility and infectious disease, leveraging historical road upgrades as a proxy for regional mobility changes. The 2009 paving of the Interoceanic Highway through the previously isolated Madre de Dios region of the Peruvian Amazon offered a natural experiment to evaluate how highway paving influences transmission of dengue virus, a high-burden mosquito-borne disease. We compared dengue incidence data from healthcare facilities near versus far from the highway before and after paving, while controlling for observable and unobservable confounding variables (a difference-in-differences causal inference approach). We found that the paving caused an additional 10,950 (95% CI: 3,186-18,715) dengue cases since 2009, a 403% (117-689%) increase in incidence rates in facilities near the highway in the 14 years since paving (2009-2022), compared to their pre-paving incidence rates. Our findings demonstrate the impact that infrastructure can have on dengue transmission, likely via its effects on human mobility. As a result, we advocate for future road construction plans in tropical regions to account for potential increases in dengue transmission during impact assessments.