The potential effects of Zika virus (ZIKV) on newborns are well-known, but a new study shows that babies exposed to the virus in utero and initially assessed as normal at birth can go on to experience delayed neurodevelopment and neurosensory alterations in the second year of life.
A team of investigators tracked a cohort of children in Rio de Janeiro, Brazil, from the time their mothers were pregnant and diagnosed with Zika during the 2015-2016 epidemic there through 32 months of age. Of the reported results for 216 infants who were studied, 31.5% had delayed neurodevelopment and/or eye abnormalities and/or hearing deficits when evaluated as late as 32 months of age. Results of the study were published in a research letter in Nature Medicine.
Karin Nielsen-Saines, MD, professor of clinical pediatrics in the Division of Infectious Diseases at UCLA Children's Hospital and lead author of the study, further explained the key findings.
“We found that 32% of children had delayed neurodevelopment and/or eye abnormalities and/or hearing deficits. We noted that 8 of these children, or 3.7%, had microcephaly; interestingly, 2 were secondary cases that developed months after birth and 2 other cases of microcephaly resolved,” she told Contagion®
Nielsen-Saines pointed out that, although nearly a third of children born without obvious structural brain abnormalities went on to experience developmental delays, including abnormal eye or hearing assessments, the opposite was also true. A previous 2016 report by the same investigators determined that 24 of 49 (49%) children with abnormal findings in early infancy had normal assessments in their second or third years of life.
“Some children who had abnormal neurologic exams in infancy turned out to be normal and others who appears normal at birth turned out to have developmental delay,” she said. “Our study underscores the need for children who were born to mothers with Zika during pregnancy to have continued monitoring in early childhood…The bottom line is that it’s not possible to predict how all Zika-exposed children will fare in the future.”
Additionally, the research team found that the timing of infection in the womb appears to have an effect on risk for below-average development.
“An earlier gestational age at the time of ZIKV infection was a significant predictor of below-average neurodevelopment,” investigators wrote. “Later gestational age at the time of ZIKV infection was less likely to be associated with below-aver-age neurodevelopment, fetal loss, and microcephaly. For each trimester by which ZIKV infection was delayed, risk for below-average development decreased by 46% (odds ratio, 0.54, adjusted; 95% confidence interval, 0.34–0.86). Eye and hearing abnormalities were not associated with gestational age of ZIKV infection.”
The next step for Nielsen-Saines and her team is to focus on the immunologic function of the children in the cohort and any possible correlation with neurodevelopment.
“These children are at risk for developmental delay and should be followed over time with close monitoring so interventions should be put in place to improve developmental outcomes,” she said.
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