Some Zika-Caused Defects Don’t Show Up Until Well After Birth

More than a year after doctors in Brazil first suspected that the Zika virus was behind a wave of babies born with deforming birth defects, new evidence suggests even babies who appear normal at birth aren’t necessarily out of the woods.

A new report by Brazilian and U.S. researchers details the cases of several Zika-infected infants who were born in northeastern Brazil with normal-size heads, but who developed microcephaly—undersized skulls that are the hallmark of Zika’s impact—within a few months. The infants’ brains...