Zika virus was found in the brain of a fetus, the strongest evidence yet that the virus causes abnormally small heads and incomplete brain development, according to an article in The New England Journal of Medicine. This is the first documented case of virus transmission from mother to child, though it is not a definitive link between Zika and fetal abnormalities — a connection first suggested by the Brazilian minister of health.
The Zika virus appeared to particularly favor neurons, today’s case report found. Damage from the virus may have halted brain development at 20 weeks, though it’s not clear how the virus was infecting nerve cells. Some structures found at autopsy showed that the virus was reproducing in the fetus’s brain.
“This is the critical point: 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 Andrew Pekosz, director of the Center for Emerging Viruses and Infectious Diseases at Johns Hopkins Bloomberg School of Public Health. “This is clear data showing Zika can infect the fetus.” Today’s case report isn’t proof that Zika is causing microcephaly, but it makes the link much likelier, Pekosz says.
The woman was a 25-year-old European volunteer who had been working in Natal, Brazil, on the country’s northeast tip. She got pregnant in February 2015; at the 13th week of pregnancy, she had a fever and rash consistent with Zika infection. Ultrasounds at 14 weeks and 20 weeks were normal.
Then, she returned to Europe at 28 weeks pregnant. An ultrasound in her 29th week showed the first signs of abnormalities. At 32 weeks, an ultrasound showed that the fetus was abnormally small — in the third percentile for fetal weight — and its head was below the second percentile for circumference. There were calcium buildups in the brain and placenta.
The woman chose to get an abortion, and doctors performed an autopsy, where they found viral replication of Zika in the fetus’s brain. The fetus was negative for 13 other viruses that may cause fetal abnormalities; the woman had no history of genetic abnormalities in her family.
The autopsy also showed severe structural abnormalities in the fetus’s brain, said study author Tatjana Avšič Županc, a microbiologist at the University of Ljubljana in Slovenia. There was a total absence of brain folds; fluid had also built up in the brain. “Our evidence means a certain danger to pregnant women, especially those in the first trimester,” Županc says. “Particularly for those who reside in or visit areas with highly endemic Zika virus.”