A single genetic change — or mutation — made the Zika virus far more dangerous, a new study suggests. That change upped the ability of the virus to kill nerve cells in the brain of a developing baby.
The mutation changed just one amino acid in a protein that the gene instructs a cell to make. That altered protein helps the Zika virus kill brain cells more easily. It also may increase the risk of a birth defect called microcephaly (My-kroh-SEFF-uh-lee). Babies born with this condition have heads and brains that are abnormally small.
Researchers reported their new results September 28 in Science.
Those scientists calculated that the mutation arose around May 2013. This was shortly before a Zika outbreak in French Polynesia. That’s a nation of islands in the South Pacific.
Mosquitoes spread the virus, which was discovered decades ago. But Zika wasn’t linked to high rates of microcephaly until a Brazil outbreak in 2015 and 2016. That’s when high numbers of women infected with Zika started giving birth to babies with small heads.
Researchers weren’t sure why Zika suddenly seemed to cause this birth defect, says Pei-Yong Shi. He is a virologist at the University of Texas Medical Branch at Galveston.
Researchers have considered several possibilities. Maybe the virus caused microcephaly before, but no one noticed. Perhaps the immune systems of people in South America just didn’t know how to fight it. Maybe they had a higher genetic risk. Or perhaps some earlier infection with a different virus somehow made Zika worse.Shi and a team in China had a different…
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