Zika can replicate in unborn babies' brains for months -- which could be why the disease is so devastating

The reason Zika has devastating consequences on unborn children could have a lot to do with the viruses’ ability to keep replicating in fetal brains.

The Centres for Disease Control and Prevention reported Tuesday that the Zika virus is able to replicate, making thousands of copies, in the brains of fetuses and in the placentas of mothers for more than seven months after the mothers contracted the virus.

The finding that the virus keeps spreading, the agency said, could help us better understand why mothers who have even mild symptoms still encounter birth defects and lost pregnancies.

“We don’t know how long the virus can persist, but its persistence could have implications for babies born with microcephaly and for apparently healthy infants whose mothers had Zika during their pregnancies,” CDC study author Julu Bhatnagar said in a news release. The study looked at tissue samples from 52 people with suspected Zika infections, which included brain tissue from eight infants born with microcephaly that later died, along with placental tissue.

One reason Zika is troubling is because it is a cause of birth defects, including microcephaly — a condition where the baby’s head is abnormally small — in babies whose mothers have had Zika. The CDC study also built on the evidence that Zika infections tend to be the most dangerous to unborn babies in the early part of the pregnancy.

Zika, which is transmitted mainly by mosquitoes, has been spreading around the world over the last year, including the US in Florida and Texas.

Once infected with Zika, only about 20% of people ever show symptoms, which most commonly include fever, rash, joint pain, and red eyes.

NOW WATCH: This animated map traces the shocking spread of Zika and where it could hit next

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