In parts of the United States where there was active transmission of Zika virus last year, there was an uptick of 21 percent in the number of babies found to have serious birth defects, scientists from the Centers for Disease Control and Prevention (CDC) have found.
The increase amounted to an additional 29 fetuses and infants in Texas, Florida, and Puerto Rico found to have birth defects affecting the central nervous system and brain, including brain, eye, and joint problems and microcephaly, or abnormally small heads. (In a typical six-month span, researchers would expect 140 infants in these regions to have these birth defects, but in June through December of 2016, local health departments reported 169.)*
"These children can have difficulty swallowing, have vision problems, difficulty sitting up, can have many seizures," says Peggy Honein, chief of the CDC's Birth Defects Branch. "This is just helping us plan for the needed public-health services for these families."
The risk is ongoing, Honein says. Based on the CDC's tracking of infections, the agency expects most Zika-affected pregnancies to have occurred throughout 2017. The CDC plans to work with local health authorities to identify affected families as long as it has funding to do so. Honein thinks there is money to analyze the data compiled through early 2017.
Zika is a virus carried by certain mosquitoes. It typically doesn't cause serious illness in adults, but when a pregnant woman is infected, there's a chance—estimated at 5 to 10 percent—that it'll cause serious problems for her fetus. Zika virus infections began showing up in the U.S. in the summer of 2016, after wreaking havoc in Central and South America. Scientists think the virus is here to stay on this continent (although, most of the time, fewer people will be infected than during those initial large outbreaks, as more folks develop immunity). The CDC recommends that pregnant women don't travel to areas where there's a risk of Zika exposure, and that pregnant women living in those regions protect themselves from mosquito bites and sexual transmission of the disease.
*UPDATE — January 26th, 2018: An earlier version of this article failed to mention Puerto Rico in its list of regions that experienced increased birth defects.