They released around 3.3 million sterile males over the 6 month study period, and found that the wild populations were reduced by 80% as a result - a level sufficient to effectively wipe out dengue fever in the area. “We saw a significant reduction in the target population”, Luke Alphey chief scientific officer and founder of Oxitec said. The GM males are engineered to die off in the wild, and so - Oxitec says - they do not pose a risk by persisting in the environment.