A large study published in June showed how a peculiar intervention could help prevent the spread of dengue fever. Instead of vaccinating people, the World Mosquito Program has found a way to breed mosquitoes carrying bacteria that prevent them catching the disease in the first place. The organisation releases millions of these designer mosquitos into a city with the aim of displacing the wild population and protecting the human residents. People Fixing the World saw the method in action in Colombia in 2019 – this is another chance to hear that report, and get an update.