Mosquitoes are essential vectors for malaria, which infects hundreds of millions each year, killing millions. Current approaches to disease prevention, which include the use of anti-malarial drugs, bed nets, repellents and vector suppression through the use of insecticides or environment modification, are insufficient.

Replacement of wild mosquito populations with genetically modified counterparts that cannot transmit disease provides another approach to disease prevention. Mosquitoes with a diminished capacity to transmit malaria have been identified in the wild and created in the laboratory, demonstrating that the mosquito immune system can be harnessed to prevent disease transmission. However, mosquitoes carrying genes that prevent malaria transmission are unlikely to have a higher fitness than native mosquitoes, and wild populations are large and dispersed over wide areas. Thus, effective population replacement will require that genes conferring disease refractoriness be linked with a genetic mechanism for spreading these genes through the wild insect population.