The prevalence of birth defects strongly linked with congenital Zika virus infection increased 21% from the first to the second half of 2016 in areas of the United States with local, endemic transmission: Puerto Rico, south Florida, and southern Texas, according to a report in the Jan. 26 edition of Morbidity and Mortality Weekly Report.
In those areas, complications strongly associated with Zika – including microcephaly; brain and eye abnormalities; and neurogenic hip dislocation, clubfoot, hearing loss, and arthrogryposis – jumped from 2.0 to 2.4 cases per 1,000 live births, with 140 cases in the first half of the year and 169 cases in the second (P = .009). Microcephaly and brain abnormalities were the most common problems.
In places with less than one confirmed Zika case from travel per 100,000 residents, such as Hawaii and Utah, the prevalence of birth defects strongly linked to Zika actually dropped from 2.8 cases per 1,000 live births to 2.4 in 2016.
The 15 U.S. jurisdictions in the study included nearly 1 million live births, representing approximately one fourth of the total live births in the United States in 2016. The live birth rate was 92% among the 2,962 infants and fetuses with Zika-associated birth defects.
All the jurisdictions had existing birth defects surveillance systems that quickly adapted to monitor for potential Zika defects. However, although strongly associated with Zika, there’s no guarantee that the birth defects in the study were actually caused by the virus, the researchers noted.
“These data will help communities plan for needed resources to care for affected patients and families and can serve as a foundation for linking and evaluating health and developmental outcomes of affected children,” said the investigators, led by Augustina Delaney, PhD, of the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention in Atlanta.
The work was the first population-based birth defect surveillance report for Zika. The CDC follows confirmed Zika cases in pregnant women and their offspring closely, but only a small portion of women are actually tested, so there’s likely far more cases of congenital Zika infection than show up in registries. Despite its limits, birth defect surveillance likely provides a more accurate picture of the actual extent of the problem.
It’s not known why Zika-linked birth defects dropped off in areas with low or no travel-associated cases. “However ... further case ascertainment from the final quarter of 2016 is anticipated in all jurisdictions,” so the numbers could change, the authors said.
They had no conflicts of interest.
SOURCE: Delaney A, et. al. MMWR Morb Mortal Wkly Rep. 2018 Jan 26;67(3):91-6