What is the Zika virus and should we be worried?

The Zika virus is a tropical disease spread by the Aedes mosquito, the same mosquito responsible for spreading yellow fever, dengue, and chikungunya. Although Zika has been around for years – it has until recently been considered as fairly harmless. That has changed in recent months, after a massive outbreak in Brazil in May last year saw more than 1 million people becoming infected across the Americas and a worrying connection between Zika and a serious birth defect, microcephaly, beginning to emerge. The disease has spread rapidly throughout the Americas since then, affecting more than thirty countries throughout South and Central America, and the Caribbean. Zika was declared a global public health emergency by the World Health Organisation (WHO) on February 1, who has warned of the virus’s potential to become a global pandemic. 

How do you catch it?

So far, Zika has been spread through the bite of the Aedes mosquito, specifically the Aedes aegypti, which is common to all the countries affected so far. The Aedes mosquito is also found across large areas of Africa and Asia, and in parts of Australia, which is one of the reasons for fears that the virus could become a global pandemic. Until now however, there have only been several cases of Zika in Europe and North America, and these seemed only to have involved people who had recently travelled to countries suffering from Zika outbreaks. Whilst it has recently been confirmed that sexual transmission of the virus is possible, only a small number of cases have occurred in this way and mosquitos remain the most important vector for the disease.

The vast majority of people affected with Zika experience no symptoms at all and may never realise they have been infected. Around 1 in 5 patients will experience symptoms similar to dengue or chikungunya, which are transmitted by the same genus of mosquito, suffering rashes, fever, muscle and joint pain, conjunctivitis or fatigue. These symptoms usually manifest 3-12 days after being bitten by an infected mosquito, and the illness generally lasts from 2 days to a week. In these cases, the disease doesn’t seem to be serious, and can be treated with general pain and fever medication, rest and plenty of fluids. 

What are the risks?

The major concern involving Zika is its role as a potential cause of microcephaly, a serious birth defect characterised by an abnormally small head and incomplete brain development. The outbreak of the virus in Brazil has been linked with an extraordinarily high number of newborns with microcephaly: over 4000 cases were reported in the country last year, compared with less than 150 in 2014. In the most severe cases microcephaly is fatal, as the brain is so underdeveloped that it is unable to regulate vital functions. Even in less severe cases, children with the condition face developmental delays and intellectual disability. Officials in Colombia, Ecuador, El Salvador and Jamaica have advised women against becoming pregnant until more is known about the connection between Zika and microcephaly, and countries including England and France have recommended that pregnant women consider delaying travel to countries with ongoing Zika outbreaks.

The best ways to protect yourself from catching Zika remain traditional anti-mosquito measures such as wearing longer clothing and using mosquito repellent and nets. There is currently no vaccine – experts expect that to develop one could take as long as 10 years – but faster and more accurate diagnostic tests are being produced so that the disease can be identified and tracked more efficiently. Scientists are also trialling the use of genetically modified sterile mosquitos to diminish the mosquito population. The theory is that sterile males released by scientists compete with wild males to mate with the female mosquitos; females who mate with the sterile males will produce no offspring, and the population of the next generation of mosquitos will be suppressed. Similar trials with varieties of fruit-fly have been very successful, but the cost alone of breeding the genetically modified mosquito in numbers sufficient to significantly affect wild mosquito populations mean that it is far from an ideal solution.

More advice for anyone who will be travelling to an area affected by Zika, or who believes they may have contracted the virus, is available here.