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The Zika virus has faded from the world’s headlines. But the damage the strange mosquito-borne virus inflicted on some children whose mothers were infected during pregnancy very much remains.

A new study, published Wednesday in the New England Journal of Medicine, reports that in a group of Zika babies from Brazil who are being followed to assess their progress, 14 percent had severe developmental problems.

This was higher than previous studies have suggested, said Dr. Karin Nielsen-Saines, one of the authors.


These children scored unusually low scores on testing of their cognition, motor, or language skills, or they had visual or hearing impairment.

“It was either both things or one or the other,” explained Nielsen-Saines, a professor of pediatric infectious diseases at the David Geffen School of Medicine at the University of California, Los Angeles.


Nielsen-Saines and her co-authors, a number of whom are from Brazil’s Oswaldo Cruz Foundation, wanted to chart what Zika would do over the long term to children born to mothers infected during pregnancy. So they followed a cohort of 182 children.

Of those, 131 were brought in by their parents for follow-up testing that involved at least one of the following: brain imaging, eye examinations, hearing tests, and a standardized test used to assess the development of children in the first few years of life. The test is called the Bayley Scales of Infant and Toddler Development, or Bayley-III.

The testing was done in the second year of life for these young children, between the ages of 12 to 18 months in most cases. Nielsen-Saines said the work is ongoing and the group is currently assessing later data from these children, who they plan to study until at least the age of 7.

Of the total, 94 of the children underwent both imaging and the Bayley-III assessment; 63 percent of them had scores that were in the normal range for cognition, motor, and language skills. But 14 percent had severe neurodevelopmental delays.

Six of the children had microcephaly and were so profoundly impacted that in essence the Bayley test could not be conducted, Nielsen-Saines said. Another roughly 15 percent had moderate developmental delays, she said.

“It sounds pretty consistent with what we’ve known. Maybe a little bit higher. But pretty consistent,” said Dr. Rita Driggers, medical director for maternal fetal medicine at Sibley Memorial Hospital in Washington, D.C., of the findings. She was not involved in the study.

Nielsen-Saines said it’s important to continue to assess these children to see if some will catch up to their peers over time or if the impairments will be lifelong.

Driggers noted that because the study is an observational one, the results have to be interpreted with a bit of caution. Parents of children who were not hitting developmental milestones might have been more inclined to bring them in for testing, effectively skewing the numbers to make the impact of Zika infection look worse.

Nielsen-Saines raised another caveat. While all of the children in the study were born to women who had tested positive for Zika infection during their pregnancies, the researchers do not know how many of the babies were actually infected in the womb. It’s known that the virus does not always cross the placenta to infect a fetus.

The report also looked at whether doctors could use brain imaging to accurately predict whether babies born to women who had been infected with Zika would go on to experience developmental delays.

The researchers found that 16 percent of children whose imaging test showed some abnormality were actually developing normally, but 2 percent of children who looked like they had normal brain scans had developmental problems.

“So maybe the imaging — especially if you’re using MRIs — might be too sensitive in picking up things that are not specific or don’t have a clinical repercussion,” Nielsen-Saines said.