EXPLAINER: The Zika Virus


Named after Uganda’s Zika Forest in 1947 after it was discovered in a species of rhesus monkey, the Zika Virus has sparked panic across the 28 countries, mostly in Latin America, where it has been found. Asymptomatic for the majority of people, there has been nervousness and uncertainty about its impact on long term health. Here biologist Dr Sheena Cruickshank from The University of Manchester clears up some of the confusion.


“There’s quite a bit of misunderstanding about Zika Virus and the first thing to clear up is that it’s usually asymptomatic.  If you get it, you are likely not to feel any symptoms. And even for those people who do have symptoms, it usually only causes mild symptoms such as conjunctivitis, joint pain, fever and rash which go away after a short time.

“It’s Brazil where much of the concern seems to be and that’s down to an apparent increase in cases of microcephaly, a condition where babies develop unusually small heads. This condition can be associated with various defects – and so is causing much concern. The problem is, it’s not clear whether the Zika virus is causing this increase. And there are a number of reasons why.


“Firstly, it’s actually quite had to link the cases of microcephaly with Zika virus because people may not have known they were infected when they were pregnant and there is very little data yet.

“And secondly, It wasn’t mandatory to report microcephaly in Brazil until 2015, and in addition to that there has been much debate about what is considered to be microcephaly: in December 2015, the Brazilian Ministry of Health significantly revised down the definition for microcephaly in newborns: reducing the head circumference from a threshold of  33 cm to 32 cm. Some people believe that some cases may not have actually been microcephaly, so there’s a lot of research to be done.


“Most people know the Zika virus is spread by mosquito bite. But it’s important to be aware that there of the 2,500 strains of mosquito, only the females from one strain has been linked to Zika. There has also been some debate over the possibility of catching Zika by sexual transmission. There have been about 3 cases so far, where there is no evidence that the person who caught the virus  travelled or was bitten by a mosquito.

This condition can be associated with various defects – and so is causing much concern. The problem is, it’s not clear whether the Zika virus is causing this increase
Dr Sheena Cruickshank


“If you’re in an area where Zika has been transmitted, or your partner has been travelled in an area where Zika has been transmitted, then it would be wise to use condoms. But the simplest thing is to avoid being bitten by a mosquito in an area that is affected by wearing long clothes and using mosquito repellent. You should also be aware of areas where the mosquitos can hatch as it likes to lay eggs in standing water. Tyres that have pooled water on their interior are actually thought to be one of the ways the mosquitos can spread, as well as for example, bird baths and small ponds.”

Notes for editors

A video of Dr Cruickshank explaining the Zika Virus is available. Anyone is welcome to embed this onto their website.


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