The mosquitoes have already been released in South America. The FDA said those mosquitoes are unlikely to harm humans, animals or the environment.

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The modified mosquitoes are designed to limit the spread of the Zika virus, which will be released soon.

The agency’s center for veterinary medicine said it found no significant impact for the trial of a method intended to reduce populations of that mosquito that spreads Zika.

While Zika is not known to be fatal, it can cause birth defects where babies can  be born with small heads and brain damage.

Since the epidemic started last spring, there have been more than 5,600 Zika cases in Brazil alone, and most cases are travel related.

The Florida Keys mosquito control district wants to conduct a trial of the mosquitoes in a small neighborhood north of Key West.