Researchers have found that Zika-related birth defects may not show up immediately at birth but can surface months later, revealing that the virus can cause hidden damage during pregnancy.
In a study of 13 babies born in Brazil, all appeared to have normal head sizes at birth, though slightly small. Over the next five to twelve months, their head growth slowed significantly, and 11 were eventually diagnosed with microcephaly. Many also developed conditions tied to Zika, including epilepsy, swallowing difficulties, muscle weakness, and joint stiffness.
Health experts say this proves that a baby without microcephaly at birth may still develop Zika-related problems. The CDC noted that this is the first detailed report of such cases. Previous research in Brazil already suggested that about one in five microcephaly cases involved babies born with head sizes in the normal range.
While the findings are troubling, they are not unexpected. Microcephaly has also appeared months after birth in infections caused by other viruses. Still, specialists warn the results may raise anxiety among parents of Zika-exposed newborns.
The CDC now advises ongoing monitoring of babies born to infected mothers and is considering whether routine imaging should be added. Researchers are also working to determine how often Zika-infected pregnant women have babies with birth defects, noting that the risk is highest when infection occurs in the first trimester and drops later in pregnancy.
