/Half of babies affected by Zika virus are developing normally by age 2

Half of babies affected by Zika virus are developing normally by age 2

Brazilian Thamires Cristina dos Santos Ferreira da Silva, 29, plays with her two-year-old son Matheus Silva, who was born with microcephaly, at their apartment in Belford Roxo, Rio de Janeiro State, Brazil, on November 30, 2018.

Brazilian Thamires Cristina dos Santos Ferreira da Silva plays with her two-year-old son Matheus who was born with microcephaly

MAURO PIMENTEL/AFP/Getty Images

Among a group of about 200 babies born to mothers who had contracted Zika virus, about one third had developmental delays, but not all of them were lasting. About half of the babies with abnormal assessments early in their lives later tested normally on developmental tests around age 2 or 3.

Karin Nielsen-Saines at the University of California, Los Angeles, and her colleagues tracked the development of babies born to women who contracted Zika virus in Rio de Janeiro, Brazil during the 2015-2016 epidemic. The 216 infants were all born by December 2016, and were assessed using standard tests to monitor infant and toddler cognition, language and motor skills. The team also tested the children’s vision and hearing.

About 30 per cent of the children had below average development, or eye or hearing deficits. Language development was the most affected, followed by motor skills and cognitive development. Eye exams were abnormal in 7 per cent of the children and hearing deficits were seen in 12 per cent of the children.

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Eight of the children had microcephaly, the abnormally small head shape associated with Zika virus, though it resolved over time in two of these cases. In one case, the child’s head naturally caught up to normal size, and in the other, the child had corrective surgery.

The team also found that 49 per cent of children with abnormal development in early infancy – including abnormal brain scans, seizures and low muscle tone – had normal results on their tests at age 2 or 3.

On the other hand, the team points out that normal assessments just after birth don’t guarantee future normal development. They found that about 25 per cent of the children in this category went on to have below average neurological development, or delays in hearing or vision development. That includes three children who developed autism by age 2.

These findings are limited by the fact that parents of children who appear healthy are often reluctant to consent to ongoing evaluations, the team writes in their paper. They also could not establish a control group of children who were definitely not exposed to Zika virus because it was highly epidemic in Rio de Janeiro and many women who may have contracted the disease did not show any symptoms and were not tested.

“As Zika is a recently recognised congenital infection, it remains to be seen whether future repercussions such as learning disabilities, further hearing loss or other problems can affect exposed children during school-age years,” the team says, so they recommend yearly assessments until age 7.

Journal reference: Nature Medicine, DOI: 10.1038/s41591-019-0496-1

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