New maps show over a third of the world is at risk of Zika outbreak
By looking at new maps, a report has revealed that more than 2 billion people are at risk of a Zika virus outbreak. This is because over a third of the world's population live in areas where the virus-spreading mosquitoes are found; including most of Southeast Asia, Sub-Saharan Africa, Northern South America, the Caribbean, the US Deep South, India, Bangladesh and Australia's far north.

On another note, besides the immediate worries over the virus, as we have previously discussed, there is a rising concern over whether Zika will cause a population gap in certain nations. Some governments, such as Brazil and Colombia, have already asked women to delay pregnancies for several months or until more is known regarding the virus. Experts warn that abrupt shifts in population can destabilise social structures, adding that countries must also plan for the inevitable population boom that will follow when the outbreak ends or a vaccine becomes available. Those countries that are affected by the virus need to move quickly if a voluntary family planning campaign is going to work.

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More than two billion people are at risk of Zika virus, experts warn, as they reveal a new map that indicates those areas at greatest risk.

The southeastern US, including much of Texas to Florida, have ideal conditions for the virus to spread.

Meanwhile, a large portion of tropical and subtropical regions also have highly suitable environmental conditions, and are on the at-risk list.

In total, these areas are inhabited by more than 2.17 billion people, scientists at the University of Oxford and the Institute for Health Metrics and Evaluation in Seattle, estimate.

Researchers produced a fine-scale global map of Zika virus transmission, as part of their study.

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Scientists at the University of Oxford have produced this new map charting the potential spread of the Zika virus across the world

They predict more than 2.17 billion people living in tropical and subtropical regions of the Americas (pictured), Africa and Asia are at risk of the virus, due to the favorable environmental conditions for the mosquitoes that carry the virus

They identified areas of the world with similar environment and socioeconomic characterstics as areas where the virus has so far been reported.

They include areas that experience precipitation and have land cover, as well as complex temperature-based virus incubation models.

Lead author, Janey Messina from Oxford University, said: 'We have comprehensively assembled all the data for Zika occurrence in humans, displayed it as a map, and combined it with detailed predictions of where the virus could spread next.

'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.'

Recent analysis has revealed the Zika virus was first introduced to Brazil in 2013, where it circulated undetected until it was eventually reported for the first time last year.

Pregnant women with Zika virus are at greater risk of giving birth to babies with microcephaly, a severe birth defect characterized by a smaller than normal head and brain damage.

There are more than 1,000 confirmed cases of Zika-associated microcephaly in Brazil, currently, and almost 5,000 suspected cases.

These new maps highlight that more than five million births in the Americas alone, will occur in areas that may be at risk of Zika over the next year.

Researchers said this demonstrates an urgent need to limit the spread of the disease and protect vulnerable populations as a matter of urgency.

An existing map provided by the US Centers for Disease Control and Prevention shows the potential range for two species of mosquito - the Aedes aegypti and the Aedes albopictus

However, it does not provide any information on whether the mosquitoes could spread disease in these areas, nor does it take into account the specifics of the latest Zika case data.

To create the current maps, the researchers focused on six variables.

Temperature is an important predictor of whether female mosquitoes can survive long enough to take a blood meal from a human and lay a batch of eggs.

It also determines whether the virus can incubate for long enough in mosquitoes - this requires about 10 days.

The researchers included data for both Ae. aegypti and Ae. albopictus, although Ae. aegypti has proven to be most effective at transmitting Zika virus.

Lead author, Janey Messina from Oxford University, said: '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'

These new maps highlight that more than five million births in the Americas alone, will occur in areas that may be at risk of Zika over the next year. Experts have warned Zika is linked to a rise in cases of the birth defect microcephaly

Higher rainfall is associated with higher infection risk for other mosquito-borne viruses of the same family, such as dengue.

The mosquitoes lay their eggs in static water.

Finally, urban areas are particularly suitable for transmitting Zika because female Ae. aegypti favour the blood of humans over other animals.

Only the females bite and transmit disease and they take regular blood meals from humans during the day to provide the nutrition needed to produce eggs.

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 Janey Messina from Oxford University

Urban areas also provide plenty of breeding sites, particularly artificial containers holding water.

The results show that although potential the range of Ae. aegypti and Ae. albopictus in the US is much larger, the focus for action should be the southeastern region, including most of Texas and the whole of Florida.

In these and other global areas on the map assessed as 'highly suitable' for transmission of the virus, an infected person could not only import the virus but risk infecting others.

The study also confirms that travel advisories are not needed for some countries - such as Uruguay, Argentine and Chile - and that transmission is likely to be confined to certain regions of others such as in Peru and Mexico.

However, the researchers warn that it is important to be cautious at this time because we are still learning more about the virus, such as the risk from sexual transmission.

The authors highlight some surprises, for example the fact that no large outbreaks have been reported in Africa or Asia despite large portions being highly suitable for transmission.

This could be due to under-reporting, misdiagnosis, or a high level of immunity in the human population, where the virus has been present for a long time.

It was first discovered in Uganda in 1947.

'Our findings that a global area inhabited by over 2.17 billion people is highly suitable for transmission of Zika virus, combined with the rapid cross-continent spread we have already seen, emphasise why the World Health Organisation has declared the current outbreak as a Public Health Emergency of International Concern,' said David Pigott from Seattle's Institute for Health Metrics and Evaluation.

'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.'