During the outbreak of the mosquito-borne Zika virus in French Polynesia, there was an increase in the rare but severe neurological condition called Guillain-Barré Syndrome (GBS). This syndrome, which can follow infection with both viruses and bacteria, causes a progressive loss of muscular power, often resulting in the patient requiring artificial ventilation as the respiratory muscles fail and breathing becomes increasingly laboured. Often necessitating long stays in intensive care units, the recovery of Guillain-Barré patients is usually protracted, with only 60% of individuals regaining full power one year after the onset of symptoms.
The Lancet paper describes a study on blood samples taken from the 42 Guillain-Barré patients during the Zika epidemic of 2013/14 in French Polynesia. As other viruses such as Dengue were circulating at the time, it was not known if Zika alone had caused the GBS increase or whether other infections had contributed. The research findings showed that the GBS patients had signs of very recent infection with Zika in their blood, and that they were infected with Zika more than the general population. It was also found that the GBS patients had in fact also been exposed to the Dengue virus, but importantly that this infection was not new. Taken together, these results provide the first evidence that Zika actually causes GBS.
The issue of whether Zika also causes the foetal developmental condition microcephaly is still unresolved, however. Clearly, it is crucial to prove causality so that funds intended to halt the increase in this serious foetal abnormality can be channelled in the most appropriate direction. The consequences of prematurely deciding that Zika causes microcephaly will not only waste valuable resources and delay the discovery of its eventual treatment, but will also allow many more needless cases of this devastating neurological condition to occur. The evidence at present, however, does strongly suggest that Zika will in fact be found to cause not only GBS, but also microcephaly.
Dr Simon Worrell, Head of Medical Communications, Healix International