Highway paving dramatically increased dengue transmission in the Amazon.

Human mobility drives the spread of many infectious diseases, yet the health impacts of changes in mobility due to new infrastructure development are poorly understood and currently not accounted for in impact assessments. We take a novel quasi-experimental approach to identifying the link between mobility and infectious disease, leveraging historical road upgrades as a proxy for regional human mobility changes. We analyzed how highway paving altered transmission of dengue-a high-burden mosquito-borne disease-via changes in human movement in the Madre de Dios region of Peru. The paving of the Interoceanic Highway through a formerly isolated region of the Amazon in 2009 provided a unique opportunity to quantify the causal impact of road paving on disease transmission. To uncover this relationship, we compared dengue incidence data from healthcare facilities in Madre de Dios near to versus far from the newly paved 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 of the highway caused at least an additional 9,826 (95% CI: 8,562-10,684) dengue cases since paving, accounting for 45.2% (95% CI: 39.4%-49.2%) of all dengue cases recorded in the region post highway paving (2009-2022). 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.