An extremely common microbe can stop the insects from spreading the virus that causes dengue fever

From the article:

Dengue fever is caused by a virus that infects an estimated 390 million people every year, and kills about 25,000; the World Health Organization has described it as one of the top 10 threats to global health. It spreads through the bites of mosquitoes, particularly the species Aedes aegypti. Utarini and her colleagues have spent the past decade turning these insects from highways of dengue into cul-de-sacs. They’ve loaded the mosquitoes with a bacterium called Wolbachia, which prevents them from being infected by dengue viruses. Wolbachia spreads very quickly: If a small number of carrier mosquitoes are released into a neighborhood, almost all of the local insects should be dengue-free within a few months. It’s as if Utarini’s team vaccinated a few individuals against a disease, and soon after the whole population had herd immunity.

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Utarini, who co-leads WMP Yogyakarta, has now shown conclusively that it [works]. Her team released Wolbachia-carrying mosquitoes in parts of Yogyakarta [Indonesia] as part of a randomized controlled trial. The results, which were unveiled last year and have now been published, showed that Wolbachia rapidly spread among the local mosquitoes, and reduced the incidence of dengue by 77 percent. “That provides the gold standard of evidence that Wolbachia is a highly effective intervention against dengue,” says Oliver Brady, a dengue expert at the London School of Hygiene and Tropical Medicine, who was not involved in the study. “It has the potential to revolutionize mosquito control.”

The trial’s results were so encouraging that the researchers have since released Wolbachia-carrying mosquitoes over all of central Yogyakarta—a 32-square-kilometer zone that’s home to more than 400,000 people. They’re now expanding into the densest surrounding provinces, aiming to protect 4 million people by the end of 2022. If they succeed, they should be able to prevent more than 10,000 dengue infections every year, Katherine Anders of the WMP told me. And the team is optimistic enough that it’s daring to think about an even grander goal: eliminating dengue from the city altogether.

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The WMP is now working in 11 countries and territories. So far, 7 million people live under the protective blanket of Wolbachia, and the organization’s goal is to cover at least 75 million by 2025, and at least half a billion by 2030. Those people won’t be protected against just dengue. Wolbachia also seems to work against the other diseases that Aedes aegypti carries, including Zika and yellow fever.