Meanwhile, in Key Haven, Florida, officials have sparked controversy with a proposal to release genetically modified mosquitoes in efforts to stop the potential spread of Zika. The genetically modified mosquitoes have been altered to carry a gene that causes the offspring to die as larva. The idea is to release the male genetically modified mosquitoes into the wild, so they will mate with female mosquitoes. The proposal has caused fierce opposition from local residents, who fear the long-term health and environmental impacts. The proposal will appear as a nonbinding referendum on the November ballot.