CDC study reveals Zika virus replicates in foetal brain and placentas


A new study by the US Centers for Disease Control and Prevention (CDC) has revealed that the Zika virus replicates in the brain tissues of infants with microcephaly and persists in foetal brains and placentas of women who suffered pregnancy losses.

Scientists from CDC found that the Zika virus ribonucleic acid (RNA) persisted for more than seven months after the mothers contracted the virus.

According to the study, the RNA levels were about 1,000 times higher in the infants’ brains than in the women’s placentas.

The study noted that the virus can make several copies of itself in the brains and placentas, which may help explain how it causes birth defects and pregnancy losses.

CDC infectious diseases pathology branch molecular pathology team lead Julu Bhatnagar said: “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.

“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's main focus is how the virus can cross the placenta and infect the foetus’s brain.

It was found that Zika infects and proliferates in Hofbauer cells in the placenta, which can move freely throughout and help transfer the virus to the foetus’s brain.

"The study noted that the virus can make several copies of itself in the brains and placentas, which may help explain how it causes birth defects and pregnancy losses."

As part of the study, tissues from 52 patients with suspected Zika virus infection, including brain tissues from eight infants with microcephaly, were tested by the researchers.

Placental tissues were also tested from 44 women and most of them were US residents who had travelled to countries with Zika outbreaks during their pregnancies.

CDC’s infectious disease pathology branch developed various tests as part of the Zika response in a bid to detect the virus in human tissue samples.

The tests can show evidence of the virus in tissues long after it would be undetectable by blood tests.


Image: Digitally colourised transmission electron micrograph of Zika virus, a member of the family Flaviviridae. Photo: courtesy of CDC / Cynthia Goldsmith.