Abstract
BACKGROUND: The introduction of the wMel strain of Wolbachia into Aedes aegypti mosquitoes significantly reduces dengue virus transmission. We evaluated the impact of large-scale releases of Wolbachia-infected Ae. aegypti on dengue incidence in Campo Grande, a large urban city in the Central-West region of Brazil, in the first deployment of Wolbachia as an official dengue-control strategy by the Brazilian federal government. METHODS: Mosquitoes infected with wMel Wolbachia were released in geographically phased deployments throughout Campo Grande from December 2020 through December 2023. An ovitrap surveillance network monitored Wolbachia prevalence in local Ae. aegypti populations during and after releases. Mixed-effects negative binomial regression was used to evaluate neighborhood-level monthly notified dengue incidence (2008-2024) as a function of monthly wMel exposure status, comparing fully treated (wMel prevalence stably ≥60%) and partially treated (ongoing releases or wMel <60%) with untreated periods, accounting for seasonal variation. FINDINGS: More than 100 million Wolbachia-infected mosquitoes were released, achieving a post-intervention mean Wolbachia prevalence of 86.4% (95% CI 84.0-88.9), with 89% of intervention areas reaching stable Wolbachia levels ≥60%. Stable establishment of wMel at ≥60% prevalence was associated with a 63.2% (95% CI 51.9-71.9) reduction in dengue incidence. INTERPRETATION: Our results demonstrate successful large-scale Wolbachia establishment in Ae. aegypti populations and a substantial epidemiological impact on dengue incidence in an urban Brazilian setting. This study provides robust evidence supporting Wolbachia deployment as an effective, sustainable public health intervention and validates its implementation as a federal government-supported dengue control strategy in Brazil. FUNDING: This work was supported by the Brazilian Ministry of Health and the Oswaldo Cruz Foundation.