An Invasive Mosquito Is Spreading With Alarming Speed, Threatening Africa’s CitiesAn invasive, malaria-carrying, insecticide-resistant mosquito that thrives in cities, where malaria has not been a major threat, has moved farther and faster across Africa than even pessimistic scientists had feared. And many public health experts believe it is too late to eliminate, or even contain, it.
A new genomic analysis of the mosquito, called Anopheles stephensi, using specimens collected from 10 countries, showed that those found in Africa had genetic resistance to all of the chemicals currently used in spraying campaigns and other mosquito-control efforts, meaning those insecticides will not kill it.
Before stephensi arrived in 2013, Djibouti was on the cusp of declaring malaria eradicated. In 2012, there were just 27 cases. A year after stephensi was found, cases shot up to nearly 1,700. Each year thereafter, the number crept up, and in 2020, there was an explosion: more than 70,000 cases.
The spread of stephensi is yet another setback in an already sputtering battle with mosquitoes in Africa. In 2024, there were nine million more malaria cases than in 2023. While the full 2025 data is not available yet, and will be less comprehensive due to health program funding cuts, there are clear signs that malaria is resurgent.
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