Zika virus plaguing South America, strongly suspected of causing malformations in babies born to infected mothers can also trigger a serious neurological disorder, Guillain-Barre syndrome, according to researchers.

This is “the first demonstration of a link between Zika and Guillain-Barre syndrome,” said Professor Arnaud Fontanet, head of the Epidemiology Unit of emerging diseases at the Pasteur Institute in Paris who coordinated the study published Tuesday in the medical journal the Lancet.

The study was conducted from data collected in French Polynesia, where Zika outbreak between October 2013 and April 2014, affected two-thirds of the population.

The disease causes, in 20 to 30% of respiratory failure and, in rich countries, about 5% of deaths. This rare neurological syndrome is observed following other viral infections (influenza, dengue, West Nile virus …) but also to a significant extent, a result of a bacterial infection (Campylobacter).

With over 1.5 million cases in Brazil, and several thousand elsewhere, which already more than 40,000 cases in Colombia , researchers warn about the risks of the outdated intensive care capacity, particularly outside urban cities .

“In areas that will be affected by the outbreak of Zika virus, think, when possible, to build capacity in intensive care because we know that a number of patients will develop a GBS among them, 30% are in need, especially for respiratory assistance, “told AFP Dr. Fontanet.

However in most cases the infection Zika virus, against which there is no vaccine or curative treatment, is benign, said epidemiologist.

Guillain-Barré syndrome (GBS), which could result in both limb paralysis and respiratory disease, was diagnosed in 42 patients, 16 of which are spent in intensive care for respiratory support. None died.

“The risk of developing Guillain-Barré syndrome has been estimated at 2.4 per 10,000 infections Zika virus,” said Dr. Fontanet.

– ‘Three evidences’ –

Researchers believe they have ruled out a role of dengue in the occurrence of these neurological damage.

They also note that a dengue infection in the past does not increase the risk of GBS among patients infected with Zika. A fear that has been expressed for the regions affected by the Zika are often as dengue.

For Professor Fontanet, the links are as strong as when we say that “smoking causes lung cancer,” even though the study does not explain the mechanism by which the virus causes the neurological syndrome.

The affirmation is based on three evidences, he said, citing the increase in cases of the syndrome during the Polynesian epidemic – their number has multiplied by twenty compared to the usual rate – and signs suggestive of infection one week Zika before the onset of neurological signs.

And, he adds, because “they found the recent presence of Zika in 100% of patients with Guillain-Barré” with blood tests looking for antibodies and “that in 93% of these patients, these antibodies were newly emerging. ”

The study was hailed by some experts. “This study provides the most compelling evidence to date of a causal link between infection with the virus Zika and neurological syndrome Guillain-Barré” said Jeremy Farrar, director of the Wellcome Trust in Britain.

“The scale of the crisis unfolding in Latin America took us all by surprise, and we must be prepared to face other unexpected complications … in the coming weeks and months,” Has -he says.

Others are more circumspect, saying that the results are not conclusive and can not be applied directly to other affected areas. “It will take a lot of work before the same conclusions can be extended to Zika epidemic in South America,” according to Peter Barlow, spokesman for the British Society for Immunology.

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