New CDC Data: Up to 40 New Cases of Zika in Pregnant Women Reported Weekly

Just in time for the warm weather and summer travel season, the Centers for Disease Control and Prevention (CDC) has some sobering news for women who are pregnant or plan to become pregnant—if they are diagnosed with Zika virus, the risk that their babies will be born with any of the birth defects associated with the mosquito-borne infection is up to 30 times higher than it would be otherwise.

This conclusion was among many significant findings included in the CDC’s Vital Signs report entitled “Protecting Pregnant Women and Babies from Zika Virus Infection,” which was published on April 4, 2017. The report analyzed data from 1000 completed pregnancies among mothers with suspected Zika infection included in the agency’s Zika Pregnancy Registry, for the period beginning January 15, 2016 and ending December 27, 2016. Only completed pregnancies reported within the 50 states and the District of Columbia were included in the analysis. In addition, data from a subset of 250 mothers with confirmed Zika virus infection were also presented.

“Although Zika may seem like last year’s problem or an issue for Brazil or Latin America, our data indicate this is not the time to be complacent,” CDC acting director Anne Schuchat, MD, said on a telebriefing held on the same day as the report’s release. “We’re still seeing about 30 to 40 new cases in pregnant women in the United States each week. The majority of these cases involve travel to Zika-affected areas. While there is much left to learn about Zika, we do know this devastating outbreak is far from over and the consequences are devastating.”

Indeed, the most recent CDC figures suggest that more than 1600 American women are suspected to have been affected with Zika, although as Dr. Schuchat and Margaret (Peggy) Honein, PhD, MPH, Chief, CDC Birth Defects Branch and co-lead, Pregnancy and Birth Defects Task Force, CDC Zika Response, noted on the call this may actually represent a fraction of the cases, as the virus remains a challenge to diagnose, given that many of those infected remain asymptomatic. It is even more challenging to assess the health of babies born to infected mothers. Although the CDC recommends brain imaging (head ultrasound or computed tomography (CT)) for all babies born to mothers who may have been exposed to the virus (via mosquitoes or sexual contact with an infected male), only roughly 1 in 4 infants undergo these tests, due to reasons concerning cost or access, or because the mothers are not aware they are ill, they said.

“Because we do not have brain imaging reports for most of the infants whose mothers had Zika during pregnancy, the current data may significantly underestimate the impact of [the virus],” Dr. Honein added.

Even with these caveats, the numbers presented by the CDC are troubling. Of the 1000 pregnancies analyzed, 51 (or 5%) resulted in babies born with Zika-related birth defects, including microcephaly and other brain abnormalities. Among those mothers with confirmed Zika infection, the incidence of these brain abnormalities was 10%. And, among those with confirmed Zika virus during the first trimester of pregnancy, 15% had babies born with Zika-related birth defects. Given that the normal incidence of these birth defects in the US population is roughly 3 per every 1000 births, according to Dr. Honein, these findings are particularly noteworthy.

Dr. Schuchat emphasized that microcephaly is not the only birth complication associated with the virus—even though it garners the most attention. Babies born to mothers infected with Zika during pregnancy can experience hearing and vision problems as well as other developmental issues, including failure to achieve growth “milestones” or difficulty using their arms and legs. Others suffer seizures. Notably, these problems do not necessarily present at birth, but may develop over time.

Dr. Schuchat also noted that these children will likely require “life-long specialized care.” It is estimated that the costs of care for infants with microcephaly could exceed $4 million. If these children reach adulthood, these costs could surpass the $10 million mark.

Brian P. Duleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.