Zika-exposed infants who had abnormalities at birth had normal test results in the second or third year of life. By contrast, a few who had normal assessments at birth had below-average developmental testing or abnormalities in hearing or vision by age 32 months, suggest researchers. 

Researchers followed 216 infants in Rio de Janeiro who had been exposed to the Zika virus during pregnancy, performing neurodevelopmental testing when the babies ranged in age from 7 to 32 months. These infants' mothers had Zika-related symptoms themselves, including rash. Although many children had normal assessments, 29 per cent scored below average in at least one domain of neurological development, including cognitive performance, fine and gross motor skills, and expressive language, wrote Sarah B Mulkey, one of the researchers of the study published in the journal of Nature Medicine. 

The study authors found progressively higher risks for developmental, hearing and eye abnormality depending on how early the pregnancy was at the time the infants were exposed. Because Zika virus has an affinity for immature neurons, even babies who were not born with microcephaly remained at continued risk for suffering abnormalities. Of note, 24 of 49 (49 per cent) infants who had abnormalities at birth went on to have normal test results in the second or third year of life. By contrast, 17 of 68 infants (25 per cent) who had normal assessments at birth had below-average developmental testing or had abnormalities in hearing or vision by age 32 months. 

"This work follows babies who were born in 2015 and 2016. It's heartening that some babies born with abnormalities tested in the normal range later in life, though it's unclear whether any specific interventions help to deliver these positive findings. And it's quite sobering that babies who appeared normal at birth went on to develop abnormalities due to that early Zika exposure," said Dr Mulkey, a fetal-neonatal neurologist. 

"This study adds to the growing body of research that argues in favour of ongoing follow-up for Zika-exposed children, even if their neurologic exams were reassuring at birth. As Zika-exposed children approach school age, it's critical to better characterise the potential implications for the education system and public health," Dr Mulkey added.