There were two different kind of mosquitos mentioned in the article. The one you are talking about are sterile males. All they do is compete with the unmodifie

There were two different kind of mosquitos mentioned in the article. The one you are talking about are sterile males. All they do is compete with the unmodified wild males, and can depress the population. As the mutation isn't passed onto any future generations, new males have to be continuously released. I remember reading somewhere else that this is already done in some places ( but I can't remember where I read it, so don't quote me on that ). The other kind mentioned in the article are non-sterile mosquitoes designed with a trait, and paired with another set of genes that cause almost all offspring to carry the same traits. I think the article mentioned around 95% of the first generation would carry the change. Pair that with a trait that causes more children to be male then female, and the population could be suppressed by only releasing one batch of altered males. To me it sounds like a really good idea, but as mentioned in the article, once released there wouldn't be any way to really control where it spread.