A single genetic mutation may have turned Zika from a boring and harmless virus into the brain-destroying guided missile that causes microcephaly and other severe birth defects, Chinese researchers said Thursday. Their findings, if they hold up, could help explain why Zika seemed to suddenly appear and tear across South and Central America, causing an epidemic of miscarriages and birth defects. Or it might not. But the intriguing study demonstrates that a single spelling error made as genetic material replicates itself could account for a profound change. Jackeline, 26, holds her son who is 4 months old and born with microcephaly, in front of their house in Olinda, near Recife, Brazil Nacho Doce / Reuters Zika was once a little-known virus, of interest to almost no one, because it didn’t cause any special symptoms in people. It was first discovered in the Ziika forest of Uganda in 1947. But then in 2015, the mosquito-borne virus was linked to an unusual increase in cases of microcephaly, a devastating birth defect in which the brain does not develop properly resulting in a smaller than normal head. Related:Zika Raises Birth Defect Rate 20 Times Its effects on babies are now indisputable as the mosquito-borne virus has spread across the Americas, causing not just microcephaly but other birth defects and also miscarriages. What hasn’t been explained is how and why it did that. Were the birth defects just never noticed before, or did the virus somehow change? Ling Yuan of the Chinese Academy of Sciences, Cheng-Feng Qin of the Beijing Institute of Microbiology and Epidemiology and colleagues set up an experiment to find out if a genetic mutation may have been responsible. They compared three currently circulating strains of Zika to a sample taken from 2010 in Cambodia, when an outbreak appeared relatively harmless. They tested mouse cells, living mice and immature human brain cells in the lab. Related: Gene Study Shows Zika Was Spreading Quietly for Years All three current strains killed all newborn mice, while the 2010 strain only killed 16 percent of them, they reported in the journal Science. They did genetic comparisons and found many differences — not an