Researchers at the Centers for Disease Control and Prevention (CDC) in collaboration with teams in the United States and Brazil have investigated the first series of infants with laboratory evidence of congenital Zika virus infection documented to be linked with the onset of microcephaly after birth.
The findings, published in the CDC’s Morbidity and Mortality Weekly Report, describe 13 infants in Brazil with congenital Zika virus infection who did not have microcephaly at birth but later experienced slowed head growth. Among these infants, 11 later developed microcephaly. The slowed head growth and microcephaly were accompanied by significant neurologic complications. Although microcephaly was not present at birth, the infants had other brain abnormalities that were consistent with congenital Zika syndrome.
The study included findings from extensive imaging, neurologic, ophthalmologic, auditory, and orthopedic examinations. All of the infants had positive tests for Zika virus–specific immunoglobulin M in cerebrospinal fluid (CSF) (nine infants), serum (two infants), or CSF and serum (two infants).
The findings indicate that among infants of mothers exposed to Zika virus during pregnancy, the absence of microcephaly at birth does not rule out congenital Zika virus infection or the presence of Zika-related brain abnormalities, according to the investigators.
The authors added that “the pathogenesis of postnatal microcephaly from congenital Zika virus infections is not known.”