These cases are the first to be reported in the UK, where the virus does not occur naturally. In the US, meanwhile, pregnant women are being warned not to head to any of the 22 countries in which the virus has been reported.
The symptoms of the mosquito-borne infection are similar to dengue and chikungunya, but are generally much milder. For the past eight months, Zika has been spreading rapidly through Africa, the Caribbean and the Americas (it was most recently reported in Puerto Rico). While the health risks posed by the disease were thought to be comparatively low, some new developments have suggested that there may be cause for more concern.
One of the possible complications of Zika is that it can cause the auto-immune disease Guillain-Barré syndrome, a potentially very severe illness. A small number of cases have been linked to this condition, first in French Polynesia and later in Brazil. While the connection is still largely theoretical, it represents another good reason to practise mosquito-bite avoidance measures in endemic areas.
More recently, Zika infections have been linked by some scientists to hundreds of cases of microcephaly in newborn babies in South America, with Brazil’s Ministry of Health reporting a notable increase in instances of microcephaly since Zika first appeared in the country last May. The neurodevelopmental disorder leads to babies being born with smaller heads and underdeveloped brains, which can cause both physical and mental disabilities. Again, the causal link is theoretical (the World Health Organization is investigating, although infectious disease specialists in Brazil are convinced that the link is not a coincidence), but the number of babies born with microcephaly that have also tested positive for Zika are said to be ‘significant’. Additionally, a Brazilian study has suggested that Zika can be transmitted between humans via breast milk, blood and semen, posing additional risks to women, children and couples attempting to conceive.