The modified mosquitoes thrived for three years, and cases of dengue were reduced by 77% in areas where they were introduced, the researchers reported in the New England Journal of Medicine.

The mosquitoes are infected with bacteria called Wolbachia, which not only interfere with the ability of viruses to live in the bodies of the insects, but which also control reproduction so that the mosquitoes only have Wolbachia-infected offspring.

The result is a growing population of insects that don't pass on viruses such as dengue, yellow fever and Zika.

The study involved more than 8,000 people, about half of whom lived in areas where the modified Aedes aegypti mosquitoes had been living and breeding.

Dengue fever was diagnosed in 9.4% of those living in areas with non-modified mosquitoes, and 2.3% of people living in areas where the modified mosquitoes had been released.