The condition is a brief but intense attack that often follows viral or bacterial infections. The U.S. National Institute of Neurological Disorders and Stroke characterizes the long-term prognosis after ADEM as “generally favorable.” However, some patients may have mild to moderate impairment, including cognitive difficulties or vision loss, for the rest of their lives. In rare cases, the condition can be fatal.
Ferreira was cautious in interpreting those preliminary findings, emphasizing that most people who experience nervous system problems with Zika do not have brain symptoms and that a definitive causal link between Zika and the ADEM has not been made.
“However, our study may shed light on possible lingering effects the virus may be associated with in the brain,” she said.
The epidemic of Zika continues to spread through the Americas, and the results of a wide scope of research only point to its increasingly grim potential. The most devastating consequences are for pregnant women, given the damage the virus is suspected of inflicting on a fetus.
In one of the first studies that sheds light on exactly how Zika attacks, researcher Patricia Garcez of the Federal University of Rio de Janeiro took human neural stem cells and infected them with virus taken from a Brazilian patient. Neural stem cells — which are able to turn into three major cell types that make up the central nervous system — are the key players in embryonic brain formation.
The outcome, published in Science on Sunday night, was unlike that of any other viruses studied by Garcez and her team. Images show a massive die-off of the stem cells, as well as greatly diminished growth for tissue used as part of a second experiment.
The team concluded that it appears Zika “targets” human brain cells. The cells they examined by electron microscope were misshapen and necrotic.
The research adds to the understanding of how the virus appears to be linked to the thousands of babies in Brazil who are being born with microcephaly, a condition marked by an abnormally small head and, in many cases, brain defects.
At the White House on Monday, top federal health officials did not play down the latest developments.
“Most of what we’ve learned is not reassuring,” said Anne Schuchat, the principal deputy director of the Centers for Disease Control and Prevention. “Everything we look at with this virus seems to be a bit scarier than we initially thought.”
She said the virus has been linked to a broader set of complications in pregnancy — not just microcephaly, but premature birth and eye problems, among others.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called the mounting neurological evidence about possible harm regardless of age “very serious.”
Health officials expressed concern about Zika’s association with a different neurological condition known as Guillain-Barré syndrome, in which the immune system attacks the nerves, sometimes leading to paralysis.
Ferreira’s research involved tracking people seen December 2014 to June 2015 who came to the hospital with a fever followed by a rash. Six people in the group experienced neurological issues, and all were confirmed to have Zika but no related viruses. Four had Guillain-Barré, and two had ADEM.
This post has been updated.