Zika : the microcéphalies would be linked to a single mutation

Felipe Dana/AP/SIPA

Published the 02.10.2017 at 18h07

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The ravages of Zika in thousands of new-born would be linked to a single mutation of the virus. This change appeared in 2013 has transformed this pathogen innocuous into a virus that is feared in the world, according to work published in Science last week.

This cousin of dengue and chikungunya has cropped up for the first time in Africa at the end of the 1940s. Responsible for a few outbreaks on this continent and in Asia decades later, the virus Zika had never revealed his dark side.

Microcephaly and malformation of brain

It is only in 2013, during a major epidemic in French Polynesia that the consequences of the virus Zika appear. The archipelago of the Pacific, which only has 270 000 inhabitants are more than 32 000 patients. Forty of them have been afflicted with Guillain-Barré syndrome (temporary paralysis) and 18 children born to infected mothers have presented congenital malformations, including microcephaly.

An explosion of cases of microcephaly is subsequently recorded in 2016 in Brazil, Colombia and all jurisdictions in which Zika spreads. Until then, the scientific world does not know how to explain why this virus became so dangerous. But a study by the chinese Academy of Sciences and Beijing university allows you to unravel the mystery.

Seven mutations suspected

By comparing the strain of Zika responsible for the epidemic of 2016 that have circulated in Cambodia in 2010, the researchers identified seven mutations. All of them seem likely to cause the neurological damage observed in children exposed in utero to the virus. However, one of them, the mutation S139N, gives Zika greater virulence and ability to cause damage to the brain of mouse fetus. Experiments carried out on human cells confirm that this mutation gives Zika the power to destroy the neurons of the fetus.

The family tree of the virus has allowed to establish that this mutation had occurred during the year 2013, either at the time of the epidemic in Polynesia.

At the present time, there is no vaccine or treatment to prevent the infection and its disastrous consequences in infants.