A British biotech company funded by Bill Gates has deployed about 150,000 genetically modified mosquitoes in the United States to reduce mosquito breeding and stop contagious diseases like dengue and malaria.

As reported by Entrepreneur, the firm, called Oxitec—funded by Bill and Melinda Gates Foundation—released the mosquitoes a week ago at Florida Keys—a chain of tropical islands in the southernmost tip of tropical Florida.

In a statement, Oxitec explained that this experiment seeks to study ways to stop the reproduction of Aedes aegypti, the main transmitters of potentially fatal diseases.

The Aedes aegypti mosquito is now living alongside half of the world’s population. Existing methods of controlling Aedes aegypti, such as spraying or fogging using chemical insecticides, have failed because the mosquito has developed resistance to insecticides, rendering many common chemicals ineffective.

According to Oxitec, this species only accounts for 4% of the mosquito population in Florida, but it is by far the most disease-transmitting species ever recorded.

Aedes aegypti mosquitoes transmit dengue, Zika, and other diseases in people and heartworm and other deadly diseases to pets and animals.

How does it work?

The males in their insect cloud have a mutated gene called OX5034 that reduces the survival rate of the females they mate with, according to the firm’s website. And as only the females in this species bite humans—only females consume blood, while males feed on nectar—thus effectively reduces the harm from this mosquito.

The firm has already tested these mosquitoes in Brazil, Malaysia, Panama and the Cayman Islands, releasing millions of modified insects into the wild. This is the first time it received regulatory approval in the U.S., India Times reported.

How to track them?

To monitor the trial’s progress, researchers would use capture devices to catch mosquitoes for the study. The mosquitos have also been given a fluorescent marker gene that causes them to glow when exposed to a certain color of light.

Oxitec intends to report the findings to the U.S. Environmental Protection Agency (EPA), which granted permission for the trial. This information will aid the EPA in determining whether Oxitech’s approach can be applied to other mosquito-infested areas across the country.