Zika Virus May Damage Infants After Birth

The Zika virus can continue to replicate and persist in the placentas of pregnant women and in the brains of infants even after birth, according to a study by the Centers for Disease Control and Prevention (CDC). The study results help to explain how the virus can be responsible for birth defects and pregnancy loss even in women who have not had a severe illness.

Seven months after mothers contracted Zika, researchers discovered Zika virus RNA in their placentas and in the brains of their fetuses. The Zika virus appeared to be replicating in one infant with microcephaly who died 2 months following birth.

“Our findings show that Zika virus can continue to replicate in infants’ brains even after birth, and that the virus can persist in placentas for months – much longer than we expected,” said Julu Bhatnagar, PhD, lead of the molecular pathology team at CDC’s Infectious Diseases Pathology Branch, said in a statement. “We don’t know how long the virus can persist, but its persistence could have implications for babies born with microcephaly and for apparently healthy infants whose mothers had Zika during their pregnancies. More studies are needed to fully understand how the virus can affect babies.”

The study examined brain tissues from 53 individuals with suspected Zika infection, including 8 infants with microcephaly who later died. Tissues from the placentas of 44 women were tested. Twenty-two of the women had adverse pregnancy or birth outcomes and 22 seemed to have healthy babies.

The 8 infants who died all tested positive for Zika virus, as did the placental tissue of 16 of the 22 women who had an adverse pregnancy or birth outcome. All of the mothers of the 8 infants, and the women with positive test results, had contracted Zika during their first trimester of pregnancy.

However, RNA from the Zika virus was also present in 8 of the 22 women who had infants who appeared healthy. These women contracted Zika during the third trimester, though the babies tested negative after birth.

"Our molecular tests for tissues extend the timeframe to detect Zika virus," Dr. Bhatnagar said. "For women who contracted Zika virus during early pregnancy but were never diagnosed, these tests could help determine whether Zika virus may have caused their miscarriage, pregnancy loss, or adverse birth outcome."

The CDC continues to recommend that clinicians monitor infants of mothers who were infected with the Zika virus during pregnancy.

—Lauren LeBano

Reference
Bhatnagar J, Rabeneck DB, Martines RB, et al. Zika Virus RNA Replication and Persistence in Brain and Placental Tissue. Emerg Infect Dis. Published online December 13, 2016.