Scientists find link between Zika virus and neurological disease

On the 1st of March 2016, a report was published in the Lancet linking the Zika virus infection to the appearance of symptoms of Guillain-Barré Syndrome (GBS).

The study exposes a rise in the prevalence of patients presenting symptoms of Guillain-Barré Syndrome following a substantial 2013-2014 outbreak of the Zika virus in French Polynesia.

Guillain-Barré is a serious neurodegenerative auto-immune disease, whereby the patient develops progressive paralysis over 1-3 weeks, which is potentially life threatening. The disease causes the  immune system to attack the conductive sheath surrounding nerves in the body, rendering them incapable of correctly transferring the nervous impulse to the muscle. Although not always fatal, its damages often cause chronic complications, as 20% of survivors develop debilitating sequelae.

Illustration of a nerve cell, its myelin sheaths visible along the tail-shaped axon.

Illustration of a nerve cell, its myelin sheaths visible along the tail-shaped axon.

Arnaud Fontanet, one of the authors of the paper and Head of the Emerging Diseases Epidemiology Unit at the Institut Pasteur, said that “this work is significant because it allows for the confirmation of the role of Zika virus infection in the occurrences of the severe neurological complications that constitute Guillain-Barré Syndrome.”

Dr. Nathalie MacDermott, paediatrician and clinical research fellow at Imperial College London, told I, Science that “what you need to remember about GBS is that it is that it is related to the host immune system.” She explains that like in the case of other GBS-triggering infections, the microbe does not cause GBS, but instead prompts the immune system to produce antibodies in order to fight off the infection. Unfortunately, the antibodies instead start attacking the nerve sheaths of the patient as an off-target effect, thus causing GBS. Therefore, Dr. MacDermott tells us that “to directly apply causation is difficult, but I think that what this study does show is that there is a link between Zika virus and GBS.”

Dr. MacDermott reassures us that “what we need to remember about Zika virus is that it is a relatively mild disease, that only one in five even show clinical symptoms.”  She adds that “yes, there appears to be an increased occurrence of GBS, but it’s only a very small number of people that are infected with Zika virus who will develop GBS, and some of that is likely down to an individual’s genetics.”

Zika virus has been the subject of intense scrutiny since end of February, when the WHO issued a Public Health Emergency of International Concern about the possible link between Zika virus epidemic and the rise of the number of cases of microcephaly reported in Brazil in 2015. Scientific evidence has not yet substantiated this causal relationship.

Dr. MacDermott reminds us that “the link between Zika virus and GBS is completely different to the possible link between Zika virus and microcephaly, and the pathogenesis would be a completely different process. The link between Zika virus and microcephaly is still being investigated.”

See the original research paper here: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2816%2900562-6/abstract

 

Marianne Guenot is studying for an MSc in Science Communication

Image: Ralwel

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