Adults infected with the Zika virus can develop a number of serious neurological conditions, a new study finds.
Until now, the most troubling Zika-related illness in adults has been Guillain-Barre syndrome, which causes muscle weakness and paralysis.
A review of 35 Zika-infected patients in Brazil with neurological symptoms found that most had Guillain-Barre. But other neurological conditions were also discovered, most often inflammation and swelling of the brain and spinal cord.
"Overall, the risk of Guillain-Barre for a person who contracts Zika is probably still very low, but it's important to know there's neurological conditions associated with Zika virus," said study co-author Dr. Jennifer Frontera. She's chief of neurology for NYU Lutheran Medical Center in New York City.
Frontera and other infectious disease experts said pregnant women still carry the most risk from Zika infection, since the virus can cause devastating neurological birth defects such as microcephaly.
Michael Osterholm is director of the University of Minnesota's Center for Infectious Disease Research and Policy in Minneapolis.
"Now we're realizing that adults may be impacted," he said. "There are clinical implications, as was well demonstrated in this paper."
The research team tracked patients who were referred to an academic hospital in Rio de Janeiro that specializes in treating neurological illnesses.
During the Zika epidemic in Brazil in 2015-16, admissions at this hospital for Guillain-Barre increased more than fivefold, Frontera said. On average, doctors there saw one case of Guillain-Barre a month before the outbreak; that rose to more than five a month as Zika raged through the country.
Out of a group of 40 patients, 35 tested positive for recent Zika infection. The Zika-affected group contained 27 people with Guillain-Barre syndrome, but also included five patients suffering from swelling of the brain (encephalitis) and two who had swelling of the spinal cord (transverse myelitis).
Another Zika-infected patient was diagnosed with chronic inflammatory demyelinating polyneuropathy, a condition closely related to Guillain-Barre that causes long-term nerve damage, muscle weakness and paralysis.
Nine of the patients required admission to an intensive care unit, and five had to be placed on a mechanical ventilator. Two patients died, including one with Guillain-Barre and one with encephalitis.
Dr. Amesh Adalja, a senior associate with the Johns Hopkins Center for Health Security said, "Follow-up studies will be important to determine the frequency of such complications and the associated risk factors. It will also be essential to definitely establish that Zika is involved as many related viruses circulate in the area in which this study was conducted."
Dr. Richard Temes is director of the Center for Neurocritical Care at North Shore University Hospital in Manhasset, N.Y. He said it makes sense that Guillain-Barre and these other conditions could appear following a Zika infection.
All of the neurological conditions researchers observed in Zika patients are "thought of as post-infectious syndromes, where you have a viral infection, you clear the infection by mounting an antibody response, and the antibodies actually attack parts of the central and peripheral nervous system, causing these neurological symptoms."
Zika spreads mainly through mosquito bite. So far, this year has been relatively calm in terms of Zika outbreaks, Osterholm said.
"This is characteristic of these infections," Osterholm said. "The virus infection comes and goes in the population. You can have a bad year or two, and then have a year where there's less infection and some people feel it's going away, which is not the case at all. It will come back. We have to understand we're in this for the long haul."
The study was published online Aug. 14 in JAMA Neurology.
To learn more about Zika and Guillain-Barre, visit the U.S. Centers for Disease Control and Prevention.
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