The Zika virus was first identified in Ugandan monkeys in 1947, and the first human case was seen in Nigeria in 1954, and there have been further outbreaks since in countries below the equator.
It is spread by the Aedes mosquito, which predominantly lives in the southern hemisphere. If the Aedes mosquito bites an infected person, it then contracts the virus, so if it then bites an uninfected person who then also has a chance of contracting the virus. If a pregnant woman becomes infected, then the baby also has a chance of contracting Zika. 


The Zika virus gives symptoms like mild fever; conjunctivitis; headache; joint pain; rashes. Deaths are rare, and only about one in five people actually develop symptoms. However, cases have recently been on the increase.


There is a suspected link to microcephaly, which affects brain development- babies are often born with an abnormally small head as their brains are not fully developed. Severity varies, but occasionally the brain can be so underdeveloped that it cannot support the functions of the body, which can lead to death. Those that do survive face disability. Microcephaly can be caused by infections such as rubella, substance abuse during pregnancy and genetic abnormalities; however some babies with microcephaly who died also had the Zika virus in their brains, and it has been detected in placenta and amniotic fluid as well.


As the numbers of those suffering from both microcephaly and the Zika virus increase in countries such as Brazil, research in potential ways to protect people from them is being undertaken. Evidence suggests that people can spread the virus via mosquitoes for around a week after being infected, and that it may persist in semen for around two weeks, leading to a call for more awareness on safe sex. Brazilian Health Minister Marcelo Castro has said that a new testing kit is being developed, and that more money is being put into developing a new vaccine. Currently insecticide is being employed in the hope of killing the mosquitoes; airplanes, for example, are being sprayed when returning from countries that may have these mosquitoes. Scientists are also trialling the use of genetically modified sterile mosquitoes to help reduce mosquito populations.


As Rio de Janeiro is the host city for the 2016 Olympic Games, efforts are being made to minimise the risk of both athletes and visitors coming into contact with the insects.