New Concern for Newborns
Researchers from the University of Wisconsin–Madison, in collaboration with the National Primate Research Center (NPRC), found that Zika exposure during pregnancy may cause developmental problems even when babies are born without obvious symptoms. The research suggests that a healthy-looking newborn may still face hidden challenges later in infancy.
The Problems Zika Brings
Zika virus is known to cause severe birth defects such as brain damage and microcephaly. However, little is understood about why 30% of babies born without physical symptoms experience developmental problems, including vision and hearing loss. To close that gap, researchers studied pregnant rhesus macaque monkeys exposed to Zika virus early in pregnancy, and followed the resulting infants for one year through behavioral tests, vision and hearing assessments and social observations.
What the Study Found
Although the infant monkeys’ eyes appeared structurally normal, researchers found disruptions in how the eyes communicated with the brain — an issue known as cortical visual dysfunction. Early visual delays appeared as early as three months of age. However, those differences resolved by the time the infants were 12 months old. Researchers also found that hearing loss appeared more often in Zika-exposed infants than in unexposed animals, though the difference was not statistically significant. Together, these findings suggest that early sensory disruptions may be a signal worth watching, even when they don’t persist.
Why Standard Screening May Not Be Enough
One of the study’s most significant findings was what didn’t predict risk. Maternal virus levels, placental infection and antibody responses did not predict which infants experienced developmental differences, suggesting that common maternal biomarkers are poor indicators of a child’s long-term risk. As study co-author and UW–Madison pediatrics professor Emma Mohr put it, “We couldn’t predict those outcomes from the mother’s infection characteristics, which is a problem if we’re trying to identify which babies need closer follow-up.”
What This Means for Families
One of the biggest takeaways is that babies exposed to Zika may need long-term developmental monitoring, even if they seem healthy at birth. Routine checkups may not catch the subtle problems that can affect learning, behavior and social development later on in life. Early screening can help families and doctors identify concerns sooner and connect children with support.
Why Prevention Still Matters
There is no vaccine for Zika, so prevention remains the best defense. Avoiding mosquito bites, using repellent, wearing protective clothing and reducing mosquito breeding sites are still important steps. For pregnant people and families planning a pregnancy, those precautions matter even more.
