We already know that Zika virus can cause a very specific birth defect called microcephaly in babies born to mothers who were infected with the virus while pregnant. While much of the funding, research, and attention has been placed on trying to prevent the spread of the virus — especially in Florida, where it has begun to make the move from Miami to Tampa — many scientists have another question on their minds: Can Zika cause brain damage in kids after they're born?
Research that confirmed the link between Zika and microcephaly (a birth defect where a baby is born with an abnormally small head, usually due to abnormal brain development in utero) also found that the virus was in the blood and tissue of the infants at birth — particularly in their brains.
This has a lot of researchers asking if its possible that Zika could cause continued brain damage in children who were infected with it while in utero, whether or not they developed microcephaly. More recent studies revealed that the virus has the potential to linger in the bodies of those babies, and their mothers, for months after birth — but what scientists don't know is if the continued presence of the virus causes more damage.
A case study in the New England Journal of Medicine, as reported by USA Today, found one case of a woman who was infected with Zika while traveling at 11 weeks pregnant. Remarkably, the virus did not clear her body until after the pregnancy was terminated at 21 weeks, after tests showed extensive brain damage in the fetus. Usually a person's immune system can clear Zika virus from their body in about a week, according to the CDC.
Another case from that same study in NEJM tested a baby throughout the first year of his life to see when the virus was finally eliminated from his blood and urine. It wasn't until he was 7 months old that he no longer had Zika in his bloodstream, but he had developed antibodies: meaning his immune system had finally been able to fend off the virus. Experts who weighed in on the case did not know exactly why the virus had lingered so long, according to USA Today.
One developing theory is that, at least while a baby is developing in utero, the virus is allowed to hang out because they're in a protected state. Generally, a woman's immune system won't attack the fetus in her uterus — but just like nutrition can pass to the fetus from the mother, so too can things like viruses pass between that barrier. So, some scientists wonder if the Zika-infected fetus continues to re-infect the mother throughout the pregnancy – either until the baby is born, the woman miscarries, or the pregnancy is terminated.
The pregnancies considered most at-risk for Zika-related complications are those where the mother is infected in the first trimester of pregnancy, the most intense time in fetal development. But there are still other complications from Zika other than microcephaly that doctors are still trying to understand — and many of them may happen later in pregnancy. Not as much is understood about how infection in the second or even third trimester can affect a baby's development, but that's where scientists are eager to begin looking — because while at some point the mother's risk decreases, science doesn't know if and when that's true of the fetus, too.
As Dr. Rita Diggers told STAT News, "At some point you’re not at risk like the fetus is. But we don’t know exactly at what age that is." While Diggers is not associated with the NEJM study, she is director of maternal fetal medicine at Sibley Memorial Hospital in Washington.
While researchers are struggling to find definitive answers about the long-term health of babies infected with Zika, they have been asking places like the CDC to follow up with pregnant women who are diagnosed with Zika to look at their health of their babies' health over time. While the information gleaned from those reports will no doubt shed light on the longterm effects of Zika on babies, it will likely take years, if not decades, for those answers to be found.