London School of Hygiene & Tropical Medicine

Evidence from French Polynesia suggests that infection with Zika virus may cause the neurological disorder Guillain-Barré syndrome, according to new research published in The Lancet.

Scientists at the Institut Pasteur in France analysed blood samples from 42 patients diagnosed with Guillain-Barré syndrome (GBS) during the largest ever outbreak of Zika virus in French Polynesia from October 2013 to April 2014. Blood tests showed that 41 (98%) of the patients were carrying Zika virus antibodies, and all (100%) had neutralising antibodies against Zika virus, providing the first evidence that infection with Zika virus may cause GBS, a severe neurological disorder.

Based on this analysis of data from French Polynesia, 24 out of 100,000 people infected with Zika virus would develop GBS, which affects the immune and nervous systems, and is the leading cause of non-trauma related paralysis. The authors note that the patients in this study generally recovered faster than is usually expected with GBS.

Commenting on the study, Jimmy Whitworth, Professor of International Public Health, London School of Hygiene & Tropical Medicine, said:

"This paper provides compelling evidence of the link between Guillain-Barré syndrome and Zika virus infection during the outbreak in French Polynesia in 2013. Guillain-Barré syndrome is a rare neurological complication seen after a variety of bacterial and viral infections (such as Campylobacter and cytomegalovirus) and occurs all around the world. From previous experience we know that one person in 2,000-4,000 of those who have had one of these infections will develop Guillain-Barré syndrome, which is an abnormal immune response to the infection. It usually occurs 2-8 weeks after an infection.

"In this paper, the authors calculate that Guillain-Barré syndrome occurred at about the same frequency after Zika virus infections as is seen with other infections. However, the condition seems to have developed sooner after infection, on average less than one week, than is seen with other infections. The affected patients are reported to have recovered quicker too. The authors found no signal that previous dengue infection was associated with the development of Guillain-Barré syndrome.

"If the experience of Zika virus infection in Latin America is similar to that seen in French Polynesia, we can expect to see about 2-5 cases of Guillain-Barré syndrome for every 10,000 people who get infected. This has implications for health care in countries with a Zika virus epidemic as a proportion of those affected with Guillain-Barré syndrome will need breathing support on a ventilator for a while, and some cases do not recover fully from the syndrome and are left with disability."

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