A technique that allows particular genes to spread rapidly through populations is not ready to be set loose in the wild, warns a committee convened by the US National Academies of Sciences, Engineering, and Medicine. In a [new] report ... the committee argued that such 'gene drives' pose complex ecological risks that are not yet fully understood. We are not ready for any kind of release," says Elizabeth Heitman, co-chair of the committee. Gene drives ... have long been postulated as a way to eradicate mosquito-borne diseases such as malaria. But the field was hampered by technical challenges until the recent advent of sophisticated - and easy-to-use - tools for engineering genomes. In the past two years, researchers have used a popular gene-editing technique called CRISPR-Cas9 to develop gene drives that spread a given gene through a population almost exponentially faster than normal. But as molecular biology research on gene drives has surged forward, it has outpaced our understanding of their ecological consequences, says Heitman. Even a small, accidental release from a laboratory holds the potential to spread around the globe: "After release into the environment, a gene drive knows no political boundaries," the committee wrote. Given this risk, the report also stressed the importance of layering multiple methods of containment to prevent accidental release of engineered species, and of consulting with the public even before gene drive experiments are undertaken in the laboratory.