The Zika virus' apparent effect on fetuses is on shocking display in a new study in the New England Journal of Medicine that was rushed to publication given the virus' spread. Though it offers no definitive link between Zika and fetal abnormalities, the study does produce the first evidence of virus transmission from mother to child and "the strongest evidence yet that the virus causes abnormally small heads and incomplete brain development," reports the Verge. The study centers on a 25-year-old Slovenian woman who became pregnant while volunteering in Brazil in February 2015. She developed a high fever and rash during her 13th week of pregnancy, but ultrasounds at 14 and 20 weeks showed no issues. When she returned to Slovenia in October, however, doctors found extensive brain damage in the fetus and the pregnancy was aborted, per NBC News.
An autopsy found the full genome of the Zika virus exclusively in the fetus' unusually smooth and scarred brain, suggesting the virus only attacked nerve tissue, per Reuters. The mother had no family history of genetic abnormalities and the fetus tested negative for 13 other viruses known to cause birth defects. "You have a mother who's infected, a fetus that's abnormal, and in the fetus, you have the genetic signature of the virus," says an infectious disease expert. "This is clear data showing Zika can infect the fetus." An epidemiologist adds "it sounds like a pretty clear case of extreme microcephaly." Scientists suspect brain development may have stopped around 20 weeks, leading one doctor to suggest that Zika, like other viruses linked to birth defects, may be most dangerous in the early stages of pregnancy. (The virus has been linked to other health problems.)