Lab technicians arrange containers of adult mosquitoes that will soon be released on Shazai Island.

PhD student and researcher Zhang Dongjing inspects trays of mosquito larvae with a small flashlight.

A worker places a container of mosquito pupae into a cage for study.

A lab worker holds a container of pupae that will soon be transferred to larger tubs.

A researcher uses a dropper to place mosquito larvae under a microscope for study.

When the project first began in 2012, scientists injected Wolbachia—known to cause reproductive problems in some bugs—into the wild eggs of Aedes Albopictus mosquitoes. Then they screened the survivors to find a female that could pass it on to her offspring and used her to breed an infected population. "All the mosquitoes we release were descended from that single mosquito," says director Zhiyong Xi.

Professor Xi Zhiyong directs the Sun Yat-Sen University-Michigan University Joint Center of Vector Control for Tropical Disease. He's standing in the Mass Production Facility, where millions of mosquitoes are bred and raised.

A lab worker scoops pupae into larger tubs, where they will grow until they reach maturity.

A lab worker shines a flashlight into a tray filled with mosquito larvae.

A technician warms animal blood on a hot plate to feed the mosquitoes.

Lab technicians use water to separate male and female larvae in the Mass Production Facility. The female larvae are easy to identify because they are larger than the males. They are thrown away, while the males are raised to adulthood.

Mosquitoes occasionally get loose at the lab, so technicians keep an electric zapping racket on hand.

A worker places containers of pupae into a cage for study.

Gan Renxian releases adult male mosquitoes on Shazai Island, a site chosen for its relative isolation. The males will mate with and infect wild females.

A villager walks home on Shazai Island, where Sunhat-Sen University-Michigan University Joint Center of Vector Control is conducting field trails.