We already knew Zika was dangerous, primarily because the virus causes brain defects in babies born to infected women. Now, a new study suggests the virus may also damage adult brain cells that help us learn and remember.
“This is the first study looking at the effect of Zika infection on the adult brain,” said Joseph Gleeson, co-author of the study and an adjunct professor at The Rockefeller University. “Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think.”
Previous reports on the spread of the virus have said symptoms were unnoticeable or generally mild. In its discussion of the health effects from Zika infection, the U.S. Centers for Disease Control and Prevention has until now cited only birth defects, pregnancy problems and an association with Guillain-Barre syndrome.
The new study presents a different possibility.
Many babies born to women infected by the Zika virus have been profoundly disabled, with brains and heads that are smaller than they should be. This condition is known as microcephaly.
Scientists from Rockefeller and the La Jolla Institute for Allergy and Immunology wondered if the virus could affect the same kind of cells in adults as they do in infants, a class of cells called neural progenitors, or brain stem cells.
They tested the idea on the brains of mice, using fluorescent biomarkers.
“Our results are pretty dramatic—in the parts of the brain that lit up, it was like a Christmas tree,” Gleeson said. “It was very clear that the virus wasn’t affecting the whole brain evenly, like people are seeing in the fetus.”
Brain stem cells, he said, “are special, and somehow very susceptible to the infection.”
The finding that Zika may target stem cells of the adult brain “closely mirrors what is seen in microcephaly,” researchers said. They called for further study of the ways the virus may target the adult brain.
Another co-author, Sujan Shresta of the La Jolla institute, said the adult brain stem cells are involved in the functions of learning and memory.
"We don't know what this would mean in terms of human diseases, or if cognitive behaviors of an individual could be impacted after infection," she said.
The story of Zika has evolved considerably since health officials first connected the proliferation of birth defects in Brazil with infection by the virus, most often spread by mosquitos.
The infection that started in South America and the Caribbean is now seen worldwide. In July, health officials in Utah announced the first U.S. death from the virus.
The CDC tracks transmission of the virus, provides updates about research and offers tips about avoiding mosquito bites. The CDC says infected people usually don’t get sick enough from Zika to go to the hospital. The most common Zika symptoms are:
- Joint pain
- Conjunctivitis, or red eyes
Symptoms can also include muscle pain and headaches, according to the CDC.
For more information
The study, “Zika Virus Infects Neural Progenitors in the Adult Mouse Brain and Alters Proliferation,” was published in the journal Cell Stem Cell. Prepared statements about the findings were published here and here.
No vaccine exists to battle the Zika virus, but you can take steps to avoid being infected. Talk to your health care provider about precautions and symptoms to watch for. You can find a Providence provider here.