With the Ebola scare behind us, the Zika virus has taken center stage as the infectious disease of the year. The culprit: mosquitoes. The crisis began in Brazil, where mosquitoes bearing the virus are thought to have arrived from Africa during the 2014 World Cup.
Though the symptoms of the virus are minor — fever, rash, joint pain, and pink eye — the implications are disastrous. If a pregnant woman is infected, her child is at risk for developing microcephaly, a rare disease in which the head is abnormally small, causing brain damage and possibly death. Brazil reports that the average of 157 cases in the past two years has skyrocketed to a staggering 2,782 so far this year. The virus has also been linked to Guillain-Barre Syndrome, a disorder in which the immune system attacks the peripheral nervous system, causing temporary paralysis and sometimes permanent nerve damage. It has spread to more than 20 countries in the Americas.
Since the virus has no medication or vaccines, its spread is difficult to prevent. Aedes mosquitoes, specifically Aedes aegypti and Aedes albopictus, carry the virus, and though the virus cannot be transmitted from person to person, a mosquito that bites someone infected with the virus can infect the next person it bites. Therefore, the Center for Disease Control and Prevention (CDC) is working on locating and destroying populations of mosquitoes, as well as encouraging pregnant women to refrain from traveling, to use repellent, and to stay indoors. Of significant concern is the fact that the upcoming summer Olympics are to be held in Brazil, where visiting competitors could easily bring the virus back to their home countries.
On January 11, the first case in the United States was reported. The Texan infected had recently traveled to Latin America, where he presumably contracted the virus. This ensued worry from Americans, as it validated the prediction of the World Health Organization that the virus was likely to “spread explosively.” Luckily, the spread of the virus is contingent on the presence of the Aedes mosquitoes as well as hot and crowded places which are conducive to its spread, so it is unlikely to cause problem in the United States.
However, the emotional effects of the epidemic are still high. For Brazilians, the virus is reminiscent of a dengue (a type of mosquito) outbreak in 2015, also caused by the Aedes mosquito. Moreover, the development of a vaccine for yellow fever, a disease caused by the Aedes mosquito as well, gave hope for the eradication of diseases transmitted by the mosquito. But a 1960 outbreak and the current Zika epidemic undermined the confidence scientists had in their ability to fight infectious disease. Fears are still reverberating throughout the Americas; Margeret Chan, director general of the WHO commented that “the level of alarm is extremely high.” After convening an emergency meeting of the WHO, Chan declared an international public health emergency on February 1.
“There is a long road ahead,” said Dr. Jeremy Farrar, director of Welcome Trust. “As with Ebola, Zika has once again exposed the world’s vulnerability to emerging infectious diseases and the devastation they can unleash. Alongside the emergency response that Zika necessitates, we must put in place the permanent reforms, health systems strengthening and proactive research agenda that are needed to make the global health system more resilient to the threat of future pandemics.”
Among the developments is a new diagnostics test that can detect the virus within a week of infection. Moreover, development of a vaccine for the Zika virus is underway. By introducing a weak or ineffective amount of the pathogen, vaccinations stimulate the immune system to produce antibodies that are needed fight the pathogens. In this way, the person does not develop the disease, but their immune system now has the ability to detect and destroy the pathogen if they ever come in contact with it. A vaccine for West Nile virus, which is caused by the same mosquito, is in progress, and researchers will use it to develop one for the Zika virus as well. A phase 1 trial, which tests the effectiveness of the vaccine, will begin with humans shortly.
Another major area of research is studying the culprit itself; scientists at Oxitec have genetically engineered mosquitoes with a lethal gene that will be passed onto their offspring. The engineered male mosquitoes, who do not bite, are dumped into affected cities, soon reproducing the lethal gene and causing the population to die out. The method proved effective in the Brazilian city of Piracicaba, population 5,000, and the company is working to produce a herd of mosquitoes that could overtake an area of 300,000 people. Researchers are also attempting to inject mosquitoes with the bacterium Wolbachia, which weakens their ability to pick up and pass on viruses.
MIT reports that another debated, but potentially extraordinary technology is the “gene drive.” A specific gene, or trait, such as one that inhibits the mosquitoes from carrying the Zika virus or one that kills out the entire population, can be introduced into mosquitoes. Normally, the offspring of a genetically engineered mosquito and a wild mosquito has a fifty percent chance of receiving the genetic change. However, when a gene drive, which consists of a guide sequence, a gene for the Cas9 enzyme, and the desired gene, is inserted into a wild mosquito, the guide sequence finds its match in the wild DNA and the Cas9 enzyme will cut out the segment of wild DNA. Then, the desired gene is replicated as the cell quickly fills in the gap in the wild DNA by using the engineered DNA as a template. Since the gene drive can essentially insert itself into wild DNA, any offspring of a mosquito with a gene drive, even if the other parent is wild, will ultimately receive the desired gene.
With all these advancements, scientists are gaining back the confidence they need to combat this epidemic head-on. They are headed in the right direction and hopefully soon another health crisis will be behind us.