A French Polynesia study has linked deadly Zika virus to Guillain-Barré syndrome (GBS), a rare but serious autoimmune disorder. Study researchers claim they have the strongest evidence till date to prove the link.

For the study published in the journal The Lancet, researchers took blood samples from 42 individuals who had GBS during the Zika virus outbreak in French Polynesia. These people with GBS were between ages 36 and 56. Approximately 90% participants were with recent Zika virus infection symptoms, said the researchers.

The study noted that within about six days, infected people started developing symptoms of Zika virus. It was the beginning of their neurological problems, it added. Zika and GBS were also linked to each other a few times ago, and in the new study, the researchers tried to examine whether the link is true.

“This is the first study to look at a large number of patients who developed Guillain-Barré syndrome following Zika virus infection and provide evidence that Zika virus can cause GBS”, said Dr. Arnaud Fontanet, director of the Centre for Global Health at the Institut Pasteur in Paris and lead author of the study.

Before the French Polynesia study, a report has established link between the Zika infection and GBS. The report cited a 40-year woman who developed muscle paralysis, mainly due to GBS, just about a week after likely becoming infected with Zika. The French Polynesia woman recovered after about 40 days, as per the researchers.

Current Zika virus outbreak has been affecting four countries- Brazil, Suriname, Colombia and El Salvador- said the World Health Organization (WHO). But the organization has also stated that it doesn’t approve a link between the Zika virus and increased incidence of GBS.