A UK-based biotech firm is developing a new weapon to kill off the dengue virus. Researchers in Brazil are producing millions of male mosquitoes genetically modified with a gene that kills off their offspring. The plan is to release the GM males into the wild where they will mate with females who will give birth to mosquitoes that carry a gene that kills them before they reach maturity. The scientist say that if done on a large scale, the dengue-carrying mosquito population could be decimated in a matter of months. Ben Gruber reports.