Fabiani de Morais Batista, Paloma M. Carcamo, Elisabeth Nelson, Antonio Brandão da Silva Neto, Daniel Henrique Tsuha, Veruska Lahdo, Vagner Ricardo dos Santos, Gabriel Sylvestre Ribeiro, Renato da Silva Lopes, Pilar Amadeu, Marcos Vinicius Ferreira Mendes Blanco, Thiago Rodrigues da Costa, Karlos Diogo de Melo Chalegre, Thais Irene Souza Riback, Cátia Cabral da Silva, Otavio T. Ranzani, Derek A.T. Cummings, Jason R. Andrews, Albert I. Ko, Matt D.T. Hitchings, Katherine L. Anders, Luciano Andrade Moreira, Crhistinne Cavalheiro Maymone Gonçalves, Julio Croda
Background The introduction of the w Mel 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 w Mel 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 w Mel exposure status, comparing fully treated ( w Mel prevalence stably ≥60%) and partially treated (ongoing releases or w Mel <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 w Mel 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.