Modern Medicine

The race is on to stop a Zika virus epidemic in the US

Daniel Bukszpan, special to
Deadly carriers of disease: Aedes aegypti mosquitoes
Paulo Whitaker | Reuters

The weather is still cold in much of the United States, so many Americans have forgotten about the dangers that can accompany warm weather. One such danger is the Zika virus, and while it may not be on many people's minds just yet, it will be again, when temperatures climb.

According to the Pan American Health Organization's most recent Regional Zika Epidemiological Update (Americas), the number of people infected with the Zika virus in the Caribbean is 651 cases per week, and in South America the weekly average is 6,601 cases, of which 6,164 were reported in Brazil alone.

In the United States more than 5,000 cases were reported between Jan. 1, 2015, and March 1, 2017. While 4,779 of these were cases in travelers returning from areas outside of the United States already known to be Zika hot spots, six cases in Texas and 215 cases in Florida were presumed to be acquired through local mosquito-borne transmission.

One company on the front lines in the Zika war is Oxitec, a biotech company in the U.K. But if you think they're working on a vaccine, you're wrong. Rather, they're creating genetically modified male Aedes aegypti mosquitoes to mate with the females who carry the disease.

According to Dr. Derric Nimmo, Oxitec's principal scientist, the company uses genetic engineering to create what they call self-limiting insects. It creates only males, as males don't bite or transmit disease. They do, however, mate with disease-carrying female Aedes aegypti insects and produce offspring that, like its genetically modified father, die before it can reach adulthood.

This means the offspring will never reach the stage in which they can carry and pass on the virus.

Trying to avoid a health catastrophe

There is currently no medicine or vaccine to prevent the disease. In June 2016 Inovia Pharmaceuticals received approval to begin human clinical trials on its Zika vaccine candidate, GLS-5700, but scientists from the University of Texas Medical Branch have said it may be as much as a decade until an FDA-approved treatment is available to the public. That's a lot of time for the virus to spread, and more than enough time for it to turn into a global threat as opposed to a regional one. So scientists at Oxitec have decided not to wait and instead to circumvent the vaccine route entirely.

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It's impossible to say how many Americans could be infected with the virus in 2017. Andrew Monaghan of the National Center for Atmospheric Research in Boulder, Colorado, helped successfully forecast the virus' transmission in Texas and Florida, and he told Science that it was likely to transmit locally in the same places in the United States where dengue is transmitted locally.

"There may be elevated risk in communities in central Florida, the Florida Keys, as well as border communities in the Rio Grande Valley in south Texas," he said in December 2016.

Growing fears of spreading Zika virus

In December 2016, the Centers for Disease Control and Prevention announced it was awarding $184 million in funding to protect Americans from the virus. It also offers a screening tool for pregnant women at its website, to be administered by health-care providers.

After conducting trials in Brazil and the Cayman Islands, Oxitec will turn its attention to the United States on an as-yet-unspecified date later in 2017, with a release of the genetically modified mosquitoes planned for the Florida Keys. This projected release has already passed a significant milestone on its way to approval.

"This was reviewed by the FDA, along with experts from the CDC and EPA, and last year they published a Finding of No Significant Impact, which stated that a trial would not have any negative impact on human health, animal health or the environment," he said.

Creating a dying breed

"Insecticides are only able to suppress the population of Aedes aegypti by 30 percent to 50 percent at best, which is not enough," said Nimmo, Oxitec's principal scientist. "In trials in urban environments in Brazil, Panama and the Cayman Islands, we have suppressed the wild population by more than 90 percent."

The virus' name is derived from the Ugandan forest where it was first isolated in 1947, and for decades it was virtually unknown in the Western Hemisphere. But authorities in Puerto Rico reported mosquito-borne transmission of the virus in human hosts in November 2015, and further cases were reported in Brazil in April 2016.

According to the Morbidity and Mortality Weekly Report, a large percentage of those infected with the virus are asymptomatic, making it easy for infected blood to make its way into the transfusion supply. Adults who do show symptoms mostly suffer from such mild and manageable complaints as headaches, fever and skin rash, but it's not the adults who see the worst of it.

The greatest danger that the virus poses is to the fetus of a pregnant woman. According to the Centers for Disease Control and Prevention, transmission of the Zika virus to an unborn baby can result in the fetal brain defect microcephaly.

Potential dangers

FDA findings aside, there are still worries about releasing genetically modified organisms into the ecosystem. In 2015 the U.K.'s House of Lords Science and Technology Committee opened an inquiry to air its ethical, regulatory and safety concerns.

"The development of GM insects is an emerging area of bioscience that presents a host of questions as well as opportunities," said Committee Chair Lord Selborne. "Concerns about lasting effects on our ecosystems and rapid spread must be considered alongside the potential opportunities for disease control and agricultural pest management."

A Miami-Dade County mosquito control inspector sprays pesticide in a Miami Beach neighborhood as the county fights to control the Zika virus outbreak on August 24, 2016.
Getty Images

Hopefully, the FDA findings will give some much needed reassurance to people living in areas plagued by the Aedes aegypti mosquitoes. In 2015, Mila de Mier, a resident of Key West, started a petition against Oxitec that was signed by 166,000 people in her community.

"Nearly all experiments with genetically modified crops have eventually resulted in unintended consequences: superweeds more resistant to herbicides, mutated and resistant insects, also collateral damage to ecosystems," she said in the petition.

"If it doesn't work, how do you recall it? I don't want my kids to be laboratory rats," she told Yale Environment 360 in June 2015.

Like it or not, the concept of genetically modified organisms carries a stigma, which has not been helped by years of horror movies about scientists' creations run amok. Nimmo said that Oxitec's creation is designed to do the exact opposite of Hollywood's big-budget nightmare scenarios.

"When people think of genetically modified organisms, they often think of an organism which has been designed to persist in the environment," he said. "Our released mosquitoes and their offspring are designed to die, so do not leave an environmental footprint. … We release modified Aedes aegypti males, which have one job – to mate with wild females."

Race against time

While worries about the genetically modified mosquitoes are understandable, the situation needs to be addressed soon. In January researchers from the University of Florida reported they had found two new disease-carrying mosquito species in the state, a sign that changes in the environment are making Florida more hospitable to tropical mosquitoes than ever.

It may also be the case that it's not just the Aedes aegypti mosquitoes that we need to worry about. A University of Georgia study published in February contained a model predicting that as many as 35 different mosquito species may be capable of transmitting Zika, and seven of those can be found in the continental United States. If the release of genetically modified insects is successful in reducing the Aedes aegypti population, then it may be a necessary tool in fighting this threat, which continues to gain strength.

Oxitec is currently waiting for final commercial approval for its mosquitoes in Brazil and the United States, which means it is not yet at the point of generating any revenue from its major commercial products. However, should it get the desired results and significantly hamper the threat of the Zika virus, then it will prove a safer and more cost-effective solution than insecticides in reducing the Aedes aegypti population.

— By Daniel Bukszpan, special to