Genetically Modified Mosquitoes: What to Know

Medically Reviewed by Minesh Khatri, MD on May 28, 2023
3 min read

It sounds like something out of a science fiction movie: a biotech company releases hundreds of thousands of genetically modified mosquitoes into the wild to control the mosquito population. But this is the real deal, a test that’s been done in a handful of countries around the world and that is underway in the U.S.

Scientists hope these bugs can help them stop the spread of some dangerous viruses over time.

There are more than 200 types of wild mosquitoes buzzing around America and the U.S. territories. One type that’s common in many parts of the country, Aedes aegypti, can spread diseases like dengue, Zika, yellow fever, and chikungunya through its bite.

Aedes aegypti mosquitoes that have had their genes changed in a lab are intended to control the disease-carrying wild ones. It’s a possible alternative to insecticides, which are used so much in the U.S. that some mosquitoes have become resistant to them, meaning they shrug off the deadly effects. And certain insecticides can be toxic to beneficial bugs like bees.

The idea is to get genetically engineered mosquitoes to do this dirty work instead.

Scientists mass produce male Aedes aegypti eggs in a lab. They program these males to carry a gene that they’ll pass to their offspring when they mate in the wild. The gene is designed to kill female offspring since only female mosquitoes bite and spread disease. The male offspring live on to pass the gene along when they mate.

Experts hope that this effort will limit the spread of mosquito-borne diseases to people over time. It’s not meant to stop an outbreak but rather to prevent one.

Pilot  tests have been done in Florida and Texas and in parts of Brazil, Panama, the Cayman Islands, and India, the CDC says. Over a billion mosquitoes have been released since 2019.

In 2022, the Environmental Protection Agency (EPA) authorized the release of up to 2.4 million modified mosquitos in several harder-hit counties in Florida and California, giving the green light to Oxitec, a biotech company based in the United Kingdom that creates genetically modified mosquitoes. The experiment ended in April 2024.

Oxitec said it plans to seek approval from California and Florida regulators to release more genetically modified Aedes aegypti mosquitos. 

For now, they’re only buzzing around the Florida Keys. There, wild Aedes aegypti make up about 4% of the mosquito population but spread almost all of the mosquito-borne disease in the area. Researchers plan to release more than 20 million mosquitoes in the Keys over the course of a few months.

They’ll track the field test’s progress with devices that trap mosquitoes to learn things like:

  • How far the genetically modified males travel
  • How long they live
  • How well the gene controls the female population

Researchers can tell lab-made mosquitoes from wild ones with a high-tech trick. They gave the genetically modified bugs a gene that makes them glow under a special red light.

Once the EPA sees the results of the test, it will decide whether Oxitec can release genetically modified mosquitoes more widely in the U.S. State and local authorities also have to sign off before the company can start a field test somewhere else. For now, the EPA has also authorized testing in counties in Texas.

The EPA studied the potential problems of releasing genetically modified mosquitoes and found “no risk to people, animals, or the environment,” according to the CDC.

The World Health Organization has put out research guidelines for genetically modified mosquitoes. They include recommendations for safety and ethics, including:

  • Standards for making decisions about how and when to do tests with the mosquitoes
  • Methods to understand potential effects on public and environmental health
  • Risk assessment strategies
  • Rules for projects to continue from one phase of testing to the next
  • Things to consider about safety and effectiveness during each stage of testing

More long-term research is needed to watch for any unforeseen effects.