Niterói is building a reputation as a model city in the face of the dengue crisis. The city's incidence rate is 187 cases per 100,000 inhabitants, seven times less than the Brazilian average.

Part of the secret is in the massive release of modified mosquitoes. They are a variant of Aedes aegypti to which the Wolbachia bacteria was introduced in the laboratory, which reduces its ability to transmit diseases such as chikungunya or yellow fever. So far this year, Brazil has recorded more than 1,100 deaths from this disease, is investigating another 1,800 and has an incidence rate of 1,460 cases per100,000 people, double that of a year ago. The World Mosquito Program breeds in a laboratory of Fiocruz (a Rio de Janeiro public health institution inspired by the Pasteur Institute) in Rio de Rio. And everything indicates that it works, says biologist Catia Cabral: “We have gone from being research, an experiment, to being an instrument of public policy”