Concern about the Zika virus is low right now, given the winter weather and decreased mosquito activity, but researchers continue to make compelling discoveries that will be important in the months ahead when the insects re-emerge.
There is new evidence the Zika virus replicates in fetal brains for up to seven months after a mother becomes infected. The virus can persist even after birth — and the first trimester may be the most worrisome time for a woman to become infected.
“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,” Julu Bhatnagar, lead of the molecular pathology team at Centers for Disease Control and Prevention’s Infectious Diseases Pathology Branch and the study’s lead author, said in a statement.
The team tested tissue from 52 patients with suspected Zika virus infection, including brain tissue from eight infants who had microcephaly and later died. They also tested placental tissues from 44 women — 22 of whom delivered apparently healthy babies and 22 whose pregnancies ended in miscarriage, abortion, or stillbirth or who delivered babies with microcephaly. Microcephaly is a rare birth defect; infants are born with undersized heads and brains and may suffer lifelong disability.
Eleven percent of the infected women were reported to have fetuses or infants with birth defects.
Zika genetic material was still evident in fetal brain tissue and placentas more than seven months after the mothers contracted the virus. In one case, evidence of the growing virus was discovered in an infant with microcephaly who died two months after birth.
Of the eight infants who had microcephaly and later died, all tested positive for Zika. The mothers of all eight of these infants contracted Zika during the first trimester of pregnancy — adding to prior evidence that Zika is most dangerous early on in pregnancy. The research is published in CDC’s Emerging Infectious Diseases journal.
Another new report outlines the impact of Zika on pregnant women in the U.S. this year. The CDC released its first analysis of data reported to the U.S. Zika pregnancy registry on Tuesday, and it showed about 6 percent of Zika-infected pregnant women had a baby or fetus with at least one birth defect related to the viral infection.
There were 442 women in the U.S. who completed their pregnancies between Jan. 15 and Sept. 22. Twenty-six of those pregnancies, or 6 percent, resulted in one or more Zika-related birth defects. But 11 percent of the women infected during their first trimester were reported to have fetuses or infants with birth defects.