Jose G. Merino, MD, MPhil


May 20, 2016

Neurologic Complications of Zika Virus

According to James Sejvar, MD, neuroepidemiologist at the Divisions of Viral and Rickettsial Disease and of Vector-Borne Infectious Diseases at the Centers for Disease Control and Prevention (CDC), "Everything we look at with this Zika virus seems to be scarier than we initially thought."

The Zika virus is a mosquito-transmitted flavivirus related to West Nile and Japanese encephalitis viruses. It was first recognized in the 1930s in Uganda and has been the cause of short-lived epidemics: In 2007, there was an outbreak in the South Pacific, and in 2013 it re-emerged in French Polynesia. In 2015[8] it was described in Brazil, and it has now spread through South and Central America. Associations with several neurologic conditions, including congenital birth defects, Guillain-Barré syndrome (GBS), meningoencephalitis, myelitis, and acute disseminated encephalomyelitis (ADEM), have been reported.

The CDC has determined[9] that Zika virus infection is a cause of microcephaly. The association was initially described in Brazil but has now been reported in other countries in the region.[10] The microcephalic pattern is consistent with the fetal brain disruption sequence, but many questions about microcephaly associated with the Zika virus remain: What is the absolute level of risk of the virus to the developing fetus? What is the timing of the highest risk? What is the spectrum of potential effects on brain development?

Another neurologic complication associated with the Zika virus is GBS,[11] which was initially identified in the 2013 outbreak in French Polynesia. In these patients, GBS was characterized by a brief prodrome, rapid progression, and a pattern suggestive of acute motor axonal neuropathy on neurophysiologic studies. There is laboratory evidence available from French Polynesia with strong evidence of association between GBS and Zika infection. An increased incidence of GBS has also been described in the current epidemic (in several countries). According to Sejvar, an investigation by the CDC and the Brazilian public health authorities shows an incidence of 7.4/100,000 patients/year. As in the cases from French Polynesia, the progression is rapid. Patients with GBS possibly associated with Zika have a severe form of GBS; 41% have required intensive care unit care, and 24% were intubated. At 6 months, 85% had ongoing motor deficits and ~50% had moderate to severe disability. But because these data come from a single study, Sejvar urged caution when interpreting the data.

Other neurologic complications have been described in association with the Zika virus epidemic (myelitis, meningoencephalitis, ADEM), and the nature of these associations is under study. The Zika virus epidemic is an evolving situation. The CDC continues to monitor and will disseminate information as it becomes available. The neurologic community must remain vigilant to identify evolving complications.


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