The rapid outbreak of mosquito-borne Zika virus across Latin America has prompted the World Health Organisation (WHO) to today declare a public health emergency of international concern.

The virus is transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions. This is the same mosquito that transmits dengue, chikungunya and yellow fever.

The current epidemic, first reported in Brazil in May 2015 and since spread to 22 other countries and territories in the region, has been linked to birth defects in Brazil and could infect as many as 4 million people in the Americas, according to WHO.

So what does all this have to do with climate change?

A number of factors have combined for the virus to spread so far and wide so quickly, but chief among them is heavy rain and heat.

These conditions, likely influenced by El Niño and possibly climate change, have helped the mosquitoes carrying Zika thrive, according to Climate Central.

While there’s been little research into the spread of Zika virus, studies on other comparable mosquito-borne diseases can help us understand how a changing climate may influence the spread of the virus.

Heavy rains in southern Brazil and Uruguay this winter (and much of the year) can translate to standing water on the ground – a crucial mosquito breeding habitat.

Meanwhile, temperatures have been above average for much of Latin America since early 2015 – which was also the hottest year on record globally, driven by climate change.

The heat delivers a double whammy for the spread of mosquito-borne diseases – as it not only means that mosquitoes can incubate the virus, but also that people are also more likely to be outside and have exposed skin for mosquitoes to feast on.

A continuing increase in average temperatures could see an increase in the geographical range of mosquitoes, and the spread of viruses they carry.

According to Climate and Health Alliance executive director Fiona Armstrong:

“Zika is the latest example of the many mosquito-borne viruses which pose an increasing threat to humans due to warmer and wetter conditions associated with climate change.”

For more information about Zika head to the WHO website, and for more on the links with climate change check out this Climate Central article.

Header image credit: Flickr user Sanofi Pasteur licensed under CC BY-NC-ND 2.0