U.S. regions where Zika is most prevalent ― including South Texas ― saw a 21-percent jump in Zika-related birth defects in the last half of 2016 compared with the first part of that year, according to a new report from the Centers for Disease Control and Prevention (CDC).
The report, which looked at nearly 1 million births in 15 U.S. states and territories, found that about three out of every 1,000 babies born in the areas studied had a birth defect associated with Zika in the mother. Of the children with anomalies, about half were born with brain abnormalities or microcephaly.
The report also found that:
- 22 percent had nervous system damage;
- 20 percent had neural tube defects and other early brain abnormalities; and
- 9 percent had eye abnormalities.
The study found a statistically significant increase in the rate of Zika-related abnormalities only in those areas ― Puerto Rico, South Florida, and the Rio Grande Valley in Texas ― where local mosquito transmission of the virus had been reported in 2016. That increase was apparent only when researchers excluded cases of “neural tube defects and other early brain malformations” from the data.
The defects seem to be tied to Zika virus, but it's not clear if Zika alone is to blame. The CDC report said other factors could have played a role. Most of the mothers of children with Zika-related birth defects were not tested for laboratory evidence of infection or test results were unknown, according to researchers.
Zika can be a difficult disease to detect. It spreads mostly by mosquito bites, though it can be passed from a pregnant woman to an unborn child. It also can spread through sexual contact or blood transfusions. Symptoms are generally mild and include fever, rash, joint pain, and conjunctivitis. However, many infected people show no symptoms at all.
CDC said many women infected in 2016 gave birth in 2017, so the 2017 data could show a similar jump in the number of birth defects.
In Texas, the study looked at births in Public Health Regions 1, 3, 9, and 11. That includes the Panhandle, the Dallas area, much of West Texas, and the Lower Rio Grande Valley. Documented local transmission of the virus occurred only in Region 11, which covers 19 counties in an area roughly south of a line from Corpus Christi to Laredo.
The Zika virus outbreak seems to have waned in Texas. According to Texas Health and Human Services, the state saw only 48 reported cases in 2017, down from 315 in 2016. South Texas counties at or near the border with Mexico reported 17 Zika cases in 2017, down from 41 in 2016.