RENEE MONTAGNE, HOST:
We've been hearing about the possible connection between the Zika Virus and a neurological condition called Guillain-Barre Syndrome. This week, NPR's Rae Ellen Bichell reports researchers came one step closer to solidifying the link.
RAE ELLEN BICHELL, BYLINE: French Polynesia is a cluster of South Pacific islands with about 270,000 residents. In late 2013, a lot of people there started getting Zika Virus.
ARNAUD FONTANET: Here in French Polynesia, two thirds of the population was infected with Zika.
BICHELL: Dr. Arnaud Fontanet is a medical epidemiologist at the Pasteur Institute in Paris. For a lot of people, he says, it was no biggie.
FONTANET: Zika is a benign disease in the vast majority of patients. It's even asymptomatic in the majority of people.
BICHELL: They didn't even know they had Zika. Some people got a rash and a fever. But a tiny portion of them - nearly 50 people - got something unsettling. A few days after the fever cleared up, they went partially paralyzed. The diagnosis - Guillain-Barre Syndrome. Fontanet is an author on a paper out this week in The Lancet that says the virus should be added to the list of causes of Guillain-Barre Syndrome. He says in a typical year, French Polynesia would only see around five cases of Guillain-Barre.
FONTANET: The increase in the number of Guillain-Barre Syndrome was 20-fold compared to the baseline rate of Guillain-Barre Syndrome they have in French Polynesia.
BICHELL: The patients spent about a month in the intensive care unit, some connected to ventilators to help them breathe. Luckily, they all lived. Three months later, most of the patients were again able to walk on their own. Fontanet and his co-authors believe that the Zika Virus had prompted the patients' immune systems to attack their own nerves. And Tahiti was a good place to study the connection. It's pretty isolated and the local clinicians were really thorough.
FONTANET: They were systematically collecting blood from the different individuals.
BICHELL: The scientists studied the blood samples from 42 patients and about four times as many controls. They found that all of the patients with Guillain-Barre syndrome had had Zika, and almost all of them had had it recently. That was different from the control groups.
FONTANET: It's actually quite strong in telling us that this was Zika virus that caused the Guillain-Barre Syndrome in those patients.
BICHELL: Further tests ruled out Dengue, another mosquito-borne disease because all groups had been equally affected by it. Dr. David Smith is a clinical virologist at the University of Western Australia. He wasn't involved in the study, but he says the results are compelling.
DAVID SMITH: Is the evidence conclusive? The answer is it hasn't reached that stage as yet, but it's strongly suggestive. So I think it's very likely that it causes Guillain-Barre Syndrome.
BICHELL: But, he points out, the French Polynesia study was small since there weren't many cases. And he says the current, much larger outbreak may solidify the connection between Zika and Guillain-Barre.
SMITH: We don't know everything we need to know yet to understand exactly why this appears to be happening and whether it's any worse in the Americas than it has been anywhere else and if it is worse, why that might be the case.
BICHELL: Among people who got Zika in French Polynesia, only about 1 in 4,000 developed Guillain-Barre. But if enough people get infected in this current outbreak, it could overwhelm hospitals. Fontanet's advice to countries dealing with Zika right now is it's important to prepare.
FONTANET: I think it is important for the countries where the epidemic now is present and active to secure intensive care beds for managing all the patients that have Guillain-Barre Syndrome because at certain time close to the peak of the epidemic, they may be saturated.
BICHELL: In the meantime, one of the looming questions for researchers is what happens in these patients that may cause such a nasty turn from what is usually an innocuous infection? Rae Ellen Bichell, NPR News.
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