When an Aedes aegypti mosquito bites someone infected with the deadly dengue virus, the virus in turn infects the mosquito. After completing its life cycle in the insect's gut, the virus makes its way into its saliva, where it can spread infection the next time the mosquito bites. But new research from Johns Hopkins University points toward a way to stop dengue from ever making it to that stage by protecting the mosquito from being infected itself.

As they described in a study in PLOS Neglected Tropical Diseases, the researchers genetically engineered Ae. aegypti to alter the production of two proteins that the mosquito naturally makes to fight off the infection. When the mosquitos were engineered to produce more of these proteins—known as Dome and Hop—in the mosquito’s version of the liver, they had fewer copies of the dengue virus in their guts once they were infected, and fewer copies in their salivary glands. They also produced fewer eggs than non-engineered mosquitos.

“If you can replace a natural population of dengue-transmitting mosquitoes with genetically modified ones that are resistant to virus, you can stop disease transmission,” lead author George Dimopoulos explains in a press release. To make the plan viable, though, the mosquitos would have to compete with their wild brethren to become the dominant mosquito type, converting the population to the disease-resistance kind of mosquito.

Unfortunately, the technique is only relevant to the transmission of dengue, so it can’t protect people from other deadly mosquito-born viruses like Zika. However, stopping dengue’s spread could prevent some 400 million deaths a year. The CDC lists dengue as a leading cause of death in tropical and subtropical regions.