The Zika virus, threatening an estimated 4 million people over 23 countries in the Americas, has generated an extremely high level of concern. Currently, there is an absence of vaccines, specific treatments and rapid diagnostic tests. The explosive spread of the virus is alarming, prompting the World Health Organisation to convene for emergency talks, but this isn’t the first time we’ve been here. Remember Ebola in West Africa, MERS in Korea, and the ongoing battle with HIV across the world, what is it about viruses that cause such concern? And why are we fundamentally incapable of effectively treating them?
The answer lies in how a virus reproduces and evolves. Unlike bacteria, a virus is essentially an inanimate, lifeless form able to hijack the body’s cells and systems. They use host systems use to multiply, making it difficult to target the virus without also attacking our own cells.
So as Zika virus rampages through the Americas, are we hopelessly doomed? No. With the onset of another virus inevitably comes the whirring of more cogs in the global research machine. As lab coats and safety goggles are donned and the search for drugs and vaccines goes on. Let’s not forget to give ourselves a pat on the back. Our own immune systems are remarkably effective at repelling foreign bodies, indeed symptoms of infection are often a result of the body fighting back rather than caused by the virus.
However, there is still a problem, vaccines and drugs for Zika are estimated to be years away and may not eradicate the disease, as other viruses such as influenza and HIV demonstrate. Both of these pathogens show how challenging our struggle is: influenza requiring a new vaccine on an annual basis while HIV‘s unique method of replication allows it to repeatedly evade our efforts through constant evolution.
When a disease can’t be cured, often the next step is to prevent it in the first place and the Zika virus is no exception. Scientists have come up with an unconventional method. The suggestion is to release mosquitos in the hope of reducing the population of A. aegypti, the mosquito species responsible for the spread of the Zika virus. Specifically, the intention is to release males with a mutated genome that causes any offspring to die before they can reproduce, therefore causing a reduction in population by up to 95% in some trials. Less mosquitos, less infections: job done. Not exactly. The genetic alteration simply dies out with the first generation of offspring and though this does placate any fears of modifications spreading throughout nature, it means GM mosquitos must be released to continuously to reduce the population
Alternatively, A. aegypti can be infected with Wolbachia, a bacteria that reduces the lifespan of a mosquito so it cannot vector a disease between humans but still live to reproduce and transmit the bacteria to it’s offspring. Initially conceptualised as a measure to combat dengue fever, also transmitted by A. aegypti, this method shows promise for combatting the spread of Zika virus, reducing populations in a trial by 65%. Following this however, the population of Wolbachia-infected mosquitos shrank, seeming to be more susceptible to insecticides.
Both methods evidently have their flaws and ultimately don’t spell the end for Zika, however in the presence of symptoms such as microcephaly in new-born children it is difficult to ignore them and as the level of risk rises to one of alarming proportions, it seems unlikely that anyone will.