Releasing Lab-Bred Mosquitoes Cut Dengue Risk by More Than 70% in Singapore

Dengue is one of the world’s fastest-spreading mosquito-borne diseases, and for years the crowded, tropical city-state of Singapore has fought it with an unusual weapon: more mosquitoes. A citywide trial published in February 2026 in The New England Journal of Medicine confirmed that the strategy works, finding that releasing lab-bred male mosquitoes carrying Wolbachia bacteria cut residents’ risk of catching dengue by more than 70%.

The study, led by researcher Jue Tao Lim, tracked 15 large residential areas over roughly two years, from mid-2022 to late 2024. In neighbourhoods where the mosquitoes were released, the population of wild female Aedes aegypti — the biting mosquitoes that actually spread dengue — fell by about 77%. Over the following three to twelve months, the risk of dengue infection dropped by roughly 71 to 72%. Among people followed for six months or more, just 6% in treated areas tested positive for a recent infection, compared with 21% in untreated areas.

“A citywide trial published in February 2026 in The New England Journal of Medicine confirmed that the strategy works, finding that releasing lab-bred male mosquitoes carrying Wolbachia bacteria cut residents’ risk of catching dengue by more than 70%.”

The method is elegant in its simplicity. Under Singapore’s Project Wolbachia, run by the National Environment Agency (NEA), male Aedes aegypti mosquitoes carrying the naturally occurring Wolbachia bacterium are released twice a week. The males do not bite and cannot transmit disease. When they mate with wild females, the resulting eggs never hatch, so each round of releases shrinks the next generation of mosquitoes. Residents are told they may notice more mosquitoes during release periods, but the extra males are harmless.

The programme is now scaling up fast. Coverage grew to about 740,000 households by March 2026 and is set to reach 800,000 — roughly half of all Singapore households — by the end of the year. The country recorded 4,036 dengue cases in 2025, its lowest tally since 2018. “NEA’s holistic dengue control strategy, which combines Project Wolbachia, vector control operations, and action by all to keep premises free of mosquito breeding, continues to help keep dengue incidence low,” said Ms Goh Hanyan, Senior Parliamentary Secretary for Sustainability and the Environment. For the many tropical cities where dengue is rising with a warming climate, Singapore’s results offer a hopeful, proven blueprint.