How Zika Virus Went From Mild to Devastating

From - September 28, 2017

How Zika Virus Went From Mild to Devastating

THURSDAY, Sept. 28, 2017 -- A single genetic mutation just a few years back gave the Zika virus the ability to cause severe neurological birth defects like microcephaly, a new study in mice suggests.

Scientists have known about the Zika virus since 1947, when it was discovered in a monkey from the Zika Forest in Uganda. At that point, it was only linked to mild symptoms.

It was not until the Zika epidemic of 2015 in Central and South America that Zika became known as a cause of microcephaly, a devastating condition in which a newborn's brain and skull are severely underdeveloped.

How did that happen?

One particular genetic change, which likely occurred in 2013, boosted Zika's ability to damage the neural stem cells that serve as building blocks for a fetus' developing brain, Chinese researchers report.

"The evidence suggests this particular mutation somehow increased the ability of the virus to get into these neural progenitor cells," said Dr. Joseph McCormick, regional dean at the University of Texas School of Public Health in Brownsville. McCormick was not involved in the new study.

This discovery is disturbing because it suggests that the virus could have more unwelcome surprises in store for humanity, said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy.

"The mutation that potentially caused this health outcome in humans is occurring in a virus where additional mutations could still occur, which could bring us other new health challenges," said Osterholm, who had no role in the research.

Zika is transmitted primarily by infected mosquitoes. It can also be spread by having sex with an infected person.

The Chinese team, whose first author is Ling Yuan of the Chinese Academy of Sciences in Beijing, compared three current Zika strains against an older strain isolated in Cambodia in 2010.

The three current strains killed all lab mice exposed to it, producing a series of neurological symptoms. On the other hand, the 2010 strain only killed about 17 percent of mice.

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