Insecticide

It was a typically anodyne statement by the World Health Organisation: "Given the magnitude of the Zika crisis, WHO encourages affected countries and their partners to boost the use of both old and new approaches to mosquito control." Anodyne, that is, until you realize what they mean by "new approaches."

Zika is a mosquito-borne virus that is spreading panic around the world. It was first linked to hydrocephaly - a developmental defect in infants that results in abnormally small heads, severe learning difficulties, and often early death - only last year in Brazil. WHO estimates that it may infect 3 million to 4 million people in the Americas alone this year - and its "new approach" is to exterminate the mosquitoes. Literally. 

An alternative approach would be to develop a vaccine for the Zika virus - but that would take up to 10 years, and the crisis is now. Zika has already been detected in 30 countries, and Brazil is investigating more than 4,300 suspected cases of microcephaly. The pressure is on to do something fast.

By the wildest of coincidences, something fast is available. It's only 12 years since Austin Burt, an evolutionary geneticist at Imperial College in London, raised the idea of a "gene drive" that would spread some desirable quality (like immunity to malaria) through an entire population in a relatively short time. With a population of mosquitoes, whose generations are only a month long, you could do it in only a year or two.

Scientists immediately set to work on mosquito genes, and by last year they had a genetically modified (GM) mosquito whose offspring do not survive into adulthood. They die as larvae, before they can breed.

By an even wilder coincidence, the species of mosquito whose genes they edited...