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The number of dengue cases <\/em>reported to the World Health Organization<\/em><\/a> (WHO) has increased eight-fold since 2000, from 500,000 cases to 4.2 million in 2019. <\/em>Wolbachia-infected Aedes mosquitoes<\/em><\/a> are bringing hope; they reduced dengue case numbers by 77 per cent during a <\/em>World Mosquito Program<\/em><\/a> (WMP) trial in Indonesia. We spoke with <\/em>Dr Katie Anders<\/em><\/a>, Director of Impact Assessment at WMP.<\/em><\/p>\n The trial divided the city of Yogyakarta into 24 communities and randomly selected 12 to receive the Wolbachia-infected mosquitoes; the other 12 showed what would have happened in the absence of Wolbachia. \u201cWe\u2019re excited about the results of our randomised controlled trial in Yogyakarta,\u201d Dr Anders told us. \u201cWhile the study supports what we see elsewhere, it is the first time we have generated solid evidence of the true impact of Wolbachia-infected Aedes<\/em> mosquitoes on dengue.\u201d<\/p>\n The study was specifically designed to stand up to scientific rigour. In addition to the control communities, the study confirmed dengue case numbers in laboratories, whereas previous trials had relied on health facilities notifying authorities of patients with the disease. Also, previous trials had struggled to exclude factors such as natural fluctuations in dengue dynamics.<\/p>\n The results are likely to be a conservative estimate of the Wolbachia effect. \u201cThe movement of people and mosquitoes across our randomly allocated communities may have diluted the result,\u201d said Dr Anders.<\/p>\n Dr Anders goes on to explain how, equally importantly, the study showed that you don\u2019t need to deploy Wolbachia-infected mosquitoes to every last square hundred metres of a city because \u201cany holes left fill themselves in over time\u201d.<\/p>\n Big cities targeted for Wolbachia-infected mosquitoes<\/em><\/p>\n WMP is currently prioritising big cities with a massive burden of disease, expanding interventions in Colombia, Brazil, Mexico and Indonesia. \u201cThe impact of Wolbachia <\/em>might be even higher deploying across a whole city,\u201d said Dr Anders. \u201cIn cities seeing tens of thousands of dengue cases, Wolbachia<\/em> offers a huge potential benefit.\u201d It aims to reach more than 75 million people over the next five years, from 5 million people to date.<\/p>\n The team plans to release mosquitoes for a second randomised controlled trial in Belo Horizonte in Brazil later this year. The trial is being run by a US-based academic group and funded by the US National Institutes of Health.<\/p>\n However, overall WMP is shifting focus from evidence generation to scaled implementation and cost-effectiveness. \u201cWe\u2019re aiming operational deployments where we can achieve the biggest impact for the lowest cost,\u201d Dr Anders explains.<\/p>\n