Genetic control methods are being developed for several major insect pest species, based on genetic modification of the insect pest followed - after considerable laboratory, regulatory and community-engagement work - by release of modified insects into target population(s). Modifications may aim to reduce the numerical size of the pest population (“population suppression”) or to reduce the vector competence of insects carrying the novel genetic trait (“refractory insects”). This talk focuses on the latter, how to reduce the ability of Aedes aegypti to transmit key viruses such as dengue virus, Zika virus and Chikungunya virus. A further practical consideration is how to get such a heritable modification into a wild vector population at a high enough allele frequency to have a significant effect on vectorial capacity, and hence potentially an epidemiological impact. While mass-release of modified insects may work well in some cases, especially for some small or accessible target populations, in many cases more self-sustaining genetic systems - gene drives - are likely essential. CRISPR/Cas9-based artificial selfish DNA elements (“gene drives”) have recently been described that might be capable of spreading through an entire species or species complex - though current designs would likely be neutralised by mutation, e.g. target site mutation, before reaching every individual. At York we are aiming to develop “local” gene drives that will sustainably modify a target population but not invade other populations of the same species. Some of the principles, progress and some limitations will be discussed.