Zika Attacked an Unborn Baby’s Brain as Doctors Watched

Doctors used MRIs and blood tests to watch, in nearly real time, as the Zika virus destroyed the brain of a fetus whose mother had been infected during a vacation in Latin America.

The nine-week ordeal of a Finnish woman who was bitten by mosquitoes during a trip to Mexico, Guatemala, and Belize is described in the New England Journal of Medicine.

The Zika virus began spreading quickly in the Americas last year and, by last fall, doctors in northeast Brazil were linking the infection to microcephaly, a devastating birth defect in which babies are born with shrunken heads and brains.

That link is now a fact. “What we do know for sure is if the fetal brain is infected, that this appears to be a very bad situation,” said Adre du Plessis, director of the Fetal Medicine Institute at the Children’s National Health System in Washington, D.C.

The woman, who lives in Washington, D.C., was 33 and three months pregnant at the time she got infected with Zika. She suffered a mild fever and rash but became concerned after reading news reports of Zika’s link to microcephaly. Over Christmas she had her blood tested in Finland.

The test, which looks for the virus’s genetic material, came back positive. But at first, ultrasound exams didn’t show any abnormality, leading Du Plessis to caution that such widely used tests may not be picking up problems.

The woman later underwent a series of MRIs, which offered a detailed and frightening picture of the baby’s brain “turning to liquid,” says Olli Vapalahti, who runs an arbovirus research center at the University of Helsinki and is the senior author of the case report.

People infected with Zika usually clear the virus in seven days, sometimes a little longer. In this case, the woman kept testing positive for the virus for just over two months. Vapalahti believes the tests were picking up the virus replicating inside the fetus’s brain tissue.

“We tracked it in real time in a way,” he says. “Our study brings hope that maybe we can screen pregnant mothers with a viral test and then do MRI studies.” Given the guarantee of severe disability, the woman chose to have an abortion at week 20.

The bigger problem is how to counsel women in less affluent parts of Latin America who won’t have access to repeated MRIs or multiple tests. In many Latin countries, access to abortion is restricted. Infection during pregnancy doesn’t always cause a birth defect; the factors that determine when microcephaly results from a Zika infection still aren’t known.

The threat of Zika seems almost existential. Yet eventually the virus may become less of a danger thanks to a phenomenon called herd immunity. That is because it’s believed that once infected, people become immune, so girls and women infected now probably won’t be at risk if they get pregnant later. Also, as fewer and fewer people are susceptible and able to spread Zika, the virus may retreat back to the forest.