Clear & present danger: Zika could affect over 2 billion people soon

You've heard of Zika. But you've probably thought it's a problem somewhere far away in a distant galaxy. It's not. The Zika virus is poised to strike at distances closer than you think. Too close for comfort.

Scientists from the University of Oxford and the Institute for Health Metrics and Evaluation, Seattle have published a research paper that includes a detailed map that shows the Zika virus transmission across countries in the world - a global 'at-risk' map, if you will.

It looks outright alarming.

The map covers a significant span of tropical and subtropical regions - amenable for the spread of the virus - and the total area is home to close to 2.17 billion people.

A mosquito-borne virus (primarily by Aedes mosquitoes), Zika was first identified in the Zika tropical forests (hence the name) of Uganda in 1947. It first came into the radar as sylvatic yellow fever was being monitored. But it was finally identified in humans in 1952 in Uganda and the United Republic of Tanzania. Later outbreaks were soon reported in Africa, the US, some Asian countries and the Pacific.

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The map, which has been published in the journal eLife, was made by locating areas of the world which are 'twins' - with similar environment and socioeconomic factors, including weather parameters.

"Our global risk map reveals priority regions where authorities could intervene to control the vector population and where surveillance of the virus should be concentrated in order to improve rapid outbreak response and clinical diagnosis." said lead author Janey Messina from the University of Oxford in a statement.

There are large tracts in Africa and Asia (including long coastal stretches in India) that could be very prone to getting affected, the study found. Long coastline stretches in South America, cities along the Amazon river and its tributaries, and significant swathes of land in the US too. In fact the US is quite high on the risk factor, though the attempt to prevent and contain the virus should mostly be in the southeastern region, including most of Texas and the whole of Florida. From Peru and Mexico to parts of India, the effect of ZIka is expected to be far and wide.

BBC quotes a researcher on the project, Dr Oliver Brady from the University of Oxford: "These are the first maps to come out that really use the data we have for Zika - earlier maps were based on Zika being like dengue or chikungunya. We are the first to add the very precise geographic and environmental conditions data we have on Zika."

There are a number of important insights that've come out of the paper - higher rainfall for example, has been associated with higher infection risk for other mosquito-borne viruses of the same family (like dengue). According to the map, a lot of urban regions are going to be very susceptible to the virus. It's because the female Ae. aegypti prefers human blood to that of other animals. They bite during the day to gain the nutrition needed for producing eggs.

In pregnant women, the virus can lead to serious complications - chances of giving birth to infants with microcephaly (underdeveloped brain). In fact, there are more than 1,000 confirmed cases of Zika-associated microcephaly in Brazil right now, and almost 5,000 suspected cases.

Another surprising highlight was that no major outbreaks have been reported in Africa or Asia despite the fact that both regions are quite vulnerable to a Zika transmission. One possible reason could be under-reporting of the disease or even misdiagnosis, both of which are grave oversights.

Countries across the world would do well to take this study seriously in order to better prepare for any large-scale emergencies in the future. Sample this: according to recent WHO data, between January 2007 and April 2016, Zika transmission was seen in a total of 64 countries and regions. Since 2015, there have been 42 countries who've experienced a ZIka outbreak with no past history of the virus there. Out of that close to six countries have reported proven cases of person-to-person transmission. The WHO has declared the current ZIka outbreak as a Public Health Emergency of International Concern.

In the context of such data and the latest study, David Pigott from Seattle's Institute for Health Metrics and Evaluation, said in a media release: 'With our maps and with the wealth of other information emerging from the global science and public health community, policy-makers can decide where to prioritise vector control and other preventative measures as well as where to be most vigilant about correctly diagnosing Zika as opposed to the many other prevalence arboviruses.'