Barcelona is releasing wolbachia mosquitoes that do not bite

Barcelona has started letting male Asian tiger mosquitoes out into two neighborhoods so that fewer mosquitoes hatch. El Mundo reported on October 16, 2026, that the Barcelona Public Health Agency is releasing about 80,000 males a week at Ciutadella Park, centered on the zoo, and at Plaça de Les Corts. The males do not bite. They carry the bacterium wolbachia, which the agency puts into tiger-mosquito eggs from a lab in Miami. Males are then sorted with an image system. When they mate with wild females that do not carry the same bacterium, the eggs do not develop.

Tomàs Montalvo, head of the agency's pest service, told El Mundo the technique is safe for people because the males neither bite nor pass on disease, and that it avoids biocides. Tiger mosquitoes can carry dengue, chikungunya, Zika, and yellow fever, but the agency said most cases found in the city were picked up abroad. The releases are meant to sit alongside the older work of emptying breeding spots and controlling larvae, not to replace it.

The pilot is there to test whether the method works and can be kept up. El Mundo did not report a drop in mosquito numbers, or in infections, from this trial.