Not only are mosquitoes annoying, but they can transmit a whole host of dangerous viruses. To tackle the mosquito-problem, the US Environmental Protection Agency (EPA) has approved the release of lab-reared mosquitoes. These mosquitoes are under-cover agents that have one goal: to kill other mosquitoes. They will be released in 20 states and Washington DC. Here’s what you need to know.

The Asian tiger mosquito Aedes albopictus is a vector for viruses, such as dengue, yellow fever, and Zika. These diseases are a large health threat and now the EPA has decided which direction they will take to reduce the threat. They have paired with the Kentucky-based biotechnology start-up MosquitoMate, which engineers special mosquitos. The mosquitoes will be raised to contain the bacterium Wolbachia pipientis and the males are sorted out from the females. Only the males, called ZAP males by the company, will be released because they don’t bite so you don’t have to worry. These males will then mate with unsuspecting wild females and produce fertilized eggs that don’t hatch because the paternal chromosomes do not form correctly. As the number of released males increases, then the total population eventually declines.

The target for elimination: Aedes albopictus. Image credits: Centers for Disease Control and Prevention’s Public Health Image Library.

The benefits are that this is a non-chemical approach and that other insects and mosquitoes are not harmed. It will still require millions and millions of mosquitos to have any effect on the population. The setback at the moment is that male and female mosquitoes are sorted by hand and mechanically. Either MosquitoMate will be putting out many jobs ads for “mosquito sorter” or have to automate the process.

This mosquito strategy is already being implemented in Guangzhou, China where 5 million Wolbachia-infected mosquitos are released each week. Their secret? They use mechanical sorters bases on the difference in size between males and females at the pupal stage, which is more than 99% efficient. The rest of the mosquitoes are sterilized with low-dose radiation that is just enough to only affect the females.

For now, the southeastern US, which has the densest mosquito populations is excluded from the trials as testing was not conducted under those climates. However, Florida has been hosting trials of the more-controversial genetically modified versions of the Zika vector, Aedes aegypti. We will see soon if this strategy is successful at reducing mosquito populations and mosquito-carried diseases.