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An increase in Guillain-Barré syndrome (GBS) cases was temporally associated with a large Zika virus outbreak in 2013–2014 in French Polynesia, where dengue virus serotypes 1 and 3 were also circulating. The incidence of GBS during the outbreak was estimated to be 0.24 cases/1000 Zika virus infections. To better understand the role of Zika virus and dengue virus infections in GBS, investigators conducted a case-control study. All GBS cases were diagnosed using international criteria by neurologists or intensive care staff at one referral hospital between November 2013 and February 2014. Control group 1 included age-, sex-, and residence-matched patients presenting with nonfebrile illnesses; control group 2 included patients with reverse transcriptase polymerase chain reaction (RT-PCR)–confirmed Zika infection without neurological complications.
Median age of the 42 GBS patients was 42 years; 74% were male. Recent viral infection was reported by 88%; median interval between viral syndrome and onset of neurological symptoms was 6 days. All received intravenous immune globulins; 38% required intensive care and 29% needed respiratory assistance. All survived.
RT-PCR on sera was negative in all GBS patients, but Zika IgM was positive in 93%, versus 17% in control group 1. Serologic evidence of past dengue infection was common and similar among the three groups. Antiglycolipid IgG antibodies, especially those directed to gangliosides, were detected in <50%. Results of nerve conduction studies suggested acute motor axonal neuropathy, but improvement during follow-up suggested reversible conduction failure.
Cao-Lormeau V-M et al. Guillain-Barré syndrome outbreak associated with Zika virus infection in French Polynesia: A case-control study. Lancet 2016 Feb 29; [e-pub]. (http://dx.doi.org/10.1016/S0140-6736(16)00562-6)
Smith DW and Mackenzie J.Zika virus and Guillain-Barré syndrome: Another viral cause to add to the list. Lancet 2016 Feb 29; [e-pub]. (http://dx.doi.org/10.1016/S0140-6736(16)00564-X)
Comment
These findings provide the best evidence to date that Zika virus can cause Guillain-Barré syndrome. However, as editorialists note, the lack of virologic confirmation and problems with cross-reactivity across flaviviruses means some serologic results might be due to dengue or other flaviviruses. Because of the absence of antiglycolipid antibodies, the authors raise the possibility of direct viral neurotoxicity. This study clearly indicates that countries experiencing Zika outbreaks need adequate intensive care facilities, especially to care for patients who require ventilator support.