Bad news: A study released Thursday in the journal Cell Stem Cell suggests Zika might, theoretically, cause some stem-cell death in adult brains too.
According to the peer-reviewed study, authored by researchers at the University of California-San Diego and New York Ciy's Rockefeller University, Zika apparently harmed some crucial stem cells in the brains of adult mice, leading researchers to speculate that the virus could harm the parts of the adult human brain that handle memory and learning.
Frighteningly, the portion of the hippocampus that Zika possibly affects — the "subgranular zone" — also plays a role in Alzheimer's disease.
"Our results suggest that ZIKV infection can enter the adult brain and lead to neuropathology in mammals," the study says.
Before anyone really freaks out, though, the study has a few big caveats. First: The researchers used only one strain of the virus and admit that other strains might not act the same way. Second: The researchers used mice, and only one type of mice, so the researchers don't even know yet if multiple mammals react the same way to Zika.
But adult brains contain some of the same stem cells that Zika affects in utero. In adult mice, the virus apparently infects parts of the hippocampus and forebrain that continue to generate new nerve cells throughout a mammal's lifespan. The study suggests that Zika infection can lead to "cell death" in adult brains and possibly slow neural growth and regeneration over time.
"Our data therefore suggest that adult as well as fetal neural stem cells are vulnerable to ZIKV neuropathology," the study says. "Thus, although ZIKV is considered a transient infection in adult humans without marked long-term effects, there may in fact be consequences of exposure in the adult brain."
The study doesn't speculate as to what those consequences might look like in, say, a 45-year-old woman or man. The "relative contribution of these features, as well as the long-term effects, on the [neural progenitor cell] niches remains unknown," the study says. (Neural progenitor cells are similar to stem cells.)
There is some good news: Scientists predict that not every mammal is susceptible to cell death, stating that it "remains a possibility that some immunocompromised humans and even some apparently health humans may be susceptible in ways modeled by the [lab-tested] mice."
The findings apparently shed some light on a phenomenon emerging in Zika-deluged nations such as Brazil: a strange, unexplained spike in cases of Guillain-Barré syndrome, a neuropathological disorder in which the body's immune system attacks its own nerves.
"Infection of [neural progenitor cells] in stem cell niches may relate to the emergent cases of Zika-linked GBS," the study states, adding it "suggests a causal relationship" between Zika and Guillain-Barré.
So, yeah, it's probably a good time to get some repellent if you haven't already.