Malaria still kills more than a million people a year. Even though low-tech measures such as spraying insecticides and distributing treated bed netting to residents can reduce infection rates, poor countries, where most victims live, cannot afford them.
As an alternative strategy, researchers have tried for years to genetically engineer mosquitoes so they will not transmit the disease. Malaria is caused by protozoan parasites that reproduce inside human liver and red blood cells and are passed from person to person by female Anopheles mosquitoes. Although several research teams managed to insert genes into lab-bred mosquitoes that made the bugs less hospitable to the parasites, the altered strains did not reproduce or survive as well as wild strains did.