Babies born with normal sized heads may face slowed skull growth and developmental problems months later.
The World Health Organization (WHO) has announced the Zika virus outbreak is no longer considered a world public health emergency. However, that doesn’t mean the virus is under control and the harm it can cause has passed — especially for babies.
A new report from the Centers for Disease Control and Prevention (CDC) found infants born to mothers infected with the virus may appear normal at first, but develop serious problems — including slowed skull growth and signs of brain injury — months later.
Zika has already been linked to a variety of health problems in babies, including seizures, spasticity, damage to eyes, and dysfunction of the brainstem. But the most feared and potentially devastating known consequence of exposure to the virus pre-birth is microcephaly, marked by a smaller than normal head size, abnormal brain development and, often, severe disabilities.
While parents understandably breathe a sigh of relief when a baby born to a Zika-exposed mom has a normal sized head, researchers have previously noted some infants whose heads measured in the normal range at birth were later diagnosed with brain defects associated with Zika . And now CDC scientists, working with researchers in Brazil, have found more evidence that head size doesn’t necessarily mean a child with congenital Zika infection is out of the woods. Instead, signs of microcephaly may develop months after birth.
The study, published in CDC’s Morbidity and Mortality Weekly Report, investigated 13 babies in Brazil with congenital Zika virus infection who experienced abnormally slow head growth over time, although they were not born with the typical smaller-than-normal head size associated with microcephaly. Despite the slowed head growth, not all of the infants developed frank microcephaly — but 11 did. And, along with their abnormally small heads, those babies diagnosed with microcephaly also developed significant neurologic complications consistent with congenital Zika syndrome.
The news Zika-caused microcephaly may develop in a baby months after birth is not totally surprising. Microcephaly is not new, although its connection with Zika was only discovered recently, and can develop over time. The condition has long been linked to certain genetic abnormalities, prenatal exposure to cytomegalovirus, rubella, drugs, and other factors — and microcephaly from these causes may be present at birth or may develop in the first few years of life, according to the National Institute of Neurological Disorders and Stroke.
Bottom line: The CDC concludes the absence of microcephaly at birth doesn’t rule out the presence of Zika-linked brain abnormalities in babies born to moms exposed to the Zika during pregnancy. So it is crucial infants who might possibly have been exposed to the virus before birth have continuing medical and developmental evaluation. The CDC also recommends early neuroimaging to look for signs of brain abnormalities in babies exposed to Zika virus prenatally.
Although the WHO no longer considers Zika a public health emergency, the organization still calls the Zika virus a significant enduring public health challenge. Many aspects of the disease and its consequences, including the impact on infants, are still not understood and need sustained research, according to a statement issued following the WHO’s latest Emergency Committee on Zika meeting.
Of course, the best course of action is to prevent Zika infection in the first place. To that end, the CDC continues to advise pregnant women to avoid places where Zika is found whenever possible. If a pregnant woman lives in an area with active Zika transmission or must travel there, she should talk with her doctor and strictly follow steps to prevent mosquito bites and sexual transmission of the virus. It’s also important for pregnant women who have possibly been exposed to the virus to be tested for Zika infection, whether or not they have any symptoms.
In addition, if you are living where Zika has been reported and you are thinking about becoming pregnant, the CDC urges you and your partner to meet with your doctor to discuss pregnancy planning so you can learn about the risks Zika poses in pregnancy and the ways to reduce them. Visit the CDC’s Women Trying to Become Pregnant page for more information.
March 31, 2020
Christopher Nystuen, MD, MBA