This post was written by Laura Malavé-Seda and Rebecca Reingold.

Photo of a mosquito

Image courtesy of SynBioBeta

Since 2015, the U.S. and U.S. territories have reported 5,074 and 38,306 cases of Zika, respectively. The Zika virus is spread to people primarily through the bite of an infected Aedes aegypti mosquito. Most people never know that they have been infected with the virus – it is estimated that four out of five people with Zika virus infections have no symptoms at all.  Even in those who develop symptoms, the illness is usually mild and, as a result, may never be diagnosed.

There is no vaccine for Zika so prevention is key. Prevention efforts have included advising people in Zika-affected areas to eliminate mosquito breeding sites, use insect repellent, wear clothes (preferably light-colored) that cover as much of the body as possible, sleep under mosquito nets, etc. However, many countries affected by Zika have struggled to control its spread, particularly during the summer months, and are exploring new prevention methods.

The UK-based biotechnology company Oxitec is testing one such method: releasing genetically modified mosquitoes to control Aedes aegypti populations. Oxitec’s approach involves injecting mosquito eggs with DNA that contains lethal genes and then releasing the genetically modified males from that batch of eggs so they can mate with wild females. According to Oxitec, the released mosquitoes and their offspring die so the genes also do not persist in the environment. Oxitec has released genetically modified mosquitoes as part of field experiments in various countries, including Brazil, the Cayman Islands, Malaysia and Panama. Based on these experiments, the company has reported that its mosquitoes can reduce the population of Aedes aegypti by 90% or more.

For five years, Oxitec, in collaboration with local officials, has been working to obtain federal approval for a trial release of its generically modified mosquitoes in the Florida Keys. In August of 2016, the U.S. Food and Drug Administration (FDA) approved the trial. Because many residents of the Keys opposed the new technology, the Florida Keys Mosquito Control District then submitted the trial to voters in the form of two nonbinding resolutions: (1) before residents of Key Haven (the community where the trials were proposed) and (2) before residents of Monroe County.

In the November election, 65% of Key Haven residents opposed the first resolution. However, 58% of residents of Monroe County voted in favor of releasing the genetically modified mosquitoes. Although the resolution is nonbinding, the Mosquito Control District has indicated it will follow the decision of the voters and has begun working with Oxitec to identify a new neighborhood to conduct trials.

While the future of genetically modified mosquitoes in the Keys remains uncertain, there is little doubt that scientists will seek other opportunities to implement and study the efficacy of this Zika prevention method, whether it is in other parts of Florida, the U.S. or the world.