The virus has been known since 1947, when it was reported in Ugandaby Philip Ball / September 19, 2016 / Leave a comment
Read more: Why we are losing the war on bugs
There’s no doubt now that the Zika virus has reached far beyond the places where it exists in the wild. Several dozen cases have now been reported in the UK, all of them in people who have travelled in Zika-infected areas, where the virus is transmitted by mosquitoes. (It may also be sexually transmitted.) For most people the risks are minimal: some never see any symptoms at all, while others experience only a rash, mild fever, and headaches before the virus is cleared from the body. But for pregnant mothers the dangers are very real: the virus seems to cause cranial shrinkage and associated neurological disorders, called microcephaly, in babies born from mothers infected with the disease.
The pandemic began in 2007, when several cases were reported in Gabon and in Micronesia—at first attributed to dengue fever, the symptoms of which are similar. In 2013 the virus had reached the islands of French Polynesia, where it is estimated to have affected about 11 per cent of the population. Then around 2013 it crossed the Pacific and entered Brazil, from where it has spread to Colombia, El Salvador, Suriname and Venezuela. There was no great international alarm, however, until the link with microcephaly started to look secure in late 2015. In rare cases, Zika can also cause the condition called Guillain-Barré syndrome, in which neural damage can cause paralysis and death.
The explosive global spread of Zika is now considered by the World Health Organisation to be a public health emergency. Its emergence in Brazil for a time seemed to threaten the 2016 Olympics, and some countries in Central America are now advising women to delay pregnancy. But within all the alarm is a puzzle. The virus has been known since 1947, when it was…