Hector Enriquez holds a glass jar above his head in Tegucigalpa, Honduras. He opens it. Buzzing, blood-sucking mosquitos swarm out. People cheer!

Wait. Who would cheer for mosquitos? Especially in a part of the world where mosquitos famously carry the deadly disease called dengue (DEN-gee) fever.

But these aren’t just any mosquitos. They’re the result of years of work. They carry bacteria called Wolbachia. When it comes to bacteria, Wolbachia is one of the good guys. It stops dengue fever in its tracks.

Dengue fever spreads most often in Southeast Asia, the western Pacific islands, Latin America, and Africa. Many people bitten by dengue-infected mosquitos grow very ill. They have flu-like symptoms. Some die. In Honduras, 10,000 people get dengue each year. The best way to not get dengue? Don’t get bitten. But mosquitos are hard to avoid. Dengue-carrying mosquitos do their biting during the daytime. Mosquito nets around beds don’t help much. And dengue vaccines don’t work on all varieties of the illness.

Over the next six months, workers will release more mosquitos. A lot more. Close to nine million more. Each bitty insect carries the Wolbachia bacteria.

How does Wolbachia work? Scientists aren’t yet sure. It also isn’t clear whether the bacteria will work equally well against all strains of dengue. But we do know this: These millions of mosquitos will have babies. The babies will be just like their moms and dads—loaded with Wolbachia.

Bless the Lord, O my soul, and forget not all His benefits, who forgives all your iniquity, who heals all your diseases. — Psalm 103:2-3

Why? Years of work can result in new ways to fight old diseases.