Areas of the U.S. with local Zika virus transmission saw a spike in related birth defects in late 2016, according to a new study.
The Centers for Disease Control and Prevention (CDC), which authored the study, called for continued surveillance.
“Babies with Zika-related birth defects need all the help they can get, as soon as possible and for as long as they need it,” CDC Director Brenda Fitzgerald, M.D., said in a news release. “This report highlights the critical importance of documenting birth defects possibly related to Zika and our need to maintain vigilance.”
CDC researchers analyzed data from 15 jurisdictions, categorizing them as areas with mosquitoes that were spreading Zika (local transmission), high rates of travel-associated cases and low rates of travel-associated cases. The results were published Thursday in the Morbidity and Mortality Weekly Report.
Among nearly 1 million infants, birth defects potentially related to Zika were found in nearly 3,000, a rate of three per 1,000 live births. Those birth defects include brain abnormalities or microcephaly (49%), neural tube defects (20%), eye abnormalities (9%) and other central nervous system dysfunction (22%). In most cases, mothers and infants were not tested for Zika on time or at all, or results were not available.
Areas with local transmission — southern Florida, southern Texas and Puerto Rico — experienced a 21% increase in children born with birth defects strongly linked to Zika during the second half of 2016 compared to the first half, which resulted in 29 more cases than expected, according to the report. This finding excluded neural tube defects, which have weak links to Zika. When those defects were included, the increase in birth defects in the second half of the year was not statistically significant.
Because local transmission peaked in the second half of the year, researchers said there also could be a spike in birth defects in the 2017 data, which were not analyzed in this report.
Prevalence of birth defects stayed the same throughout 2016 in areas with high rates travel-associated cases and declined in areas with low rates of travel-associated cases. Researchers said the cause of the decline is unclear.
Pediatricians should report suspected congenital Zika virus cases to their local health department and provide information to the CDC’s Zika Pregnancy and Infant Registry.
“These data will help communities plan for needed resources to care for affected patients and families,” the authors wrote, “and can serve as a foundation for linking and evaluating health and developmental outcomes of affected children.”