ROBERT SIEGEL, HOST:
Zika may seem like last year's problem, but the Centers for Disease Control and Prevention says it's not. The CDC published a study this week on where we are with Zika in the U.S., and the findings are striking. Joining us is Margaret Honein of the CDC who led the study. Welcome to the program.
MARGARET HONEIN: Thank you very much.
SIEGEL: And if you could, please catch us up on where we are with Zika in the U.S. How many cases in pregnant women do we know about, and have they been concentrated in any particular parts of the country?
HONEIN: Right. So during 2016, there were nearly a thousand pregnancies completed and had lab evidence of possible Zika. But as of today's update, there's over 1,700 pregnant women with Zika that have been reported to the U.S. Zika Pregnancy Registry.
SIEGEL: Spread throughout the United States or concentrated in the South - where are they?
HONEIN: So there's been pregnant women reported from 44 different states in the U.S. There are some areas that have more travelers. We know that there have been, you know, in Florida and Texas some local transmission of Zika. But largely, this is all across the U.S. Almost every state has at least one pregnant woman with Zika.
SIEGEL: Your study says that there were 51 babies born with birth defects in the U.S. last year because their mothers were infected with Zika. Were any of these mothers infected in the U.S. or are these all cases of women contracting Zika while traveling abroad?
HONEIN: So among the 51 in this report that had one of these Zika-associated birth defects, they acquired Zika from 16 different countries and territories. None of those were in the continental U.S.
SIEGEL: Now that Zika's been around for a while, do we know more about the range of problems that it causes?
HONEIN: We're learning more every day about the range of the birth defects, but we do know that it causes these serious brain abnormalities. It can cause problems with vision, problems with hearing. And there are other consequences, like these very stiff joints that can require lifelong, specialized care for these babies.
SIEGEL: But just to be clear, just because a woman is infected with Zika, and even if she's pregnant, doesn't necessarily mean that she'd have these outcomes.
HONEIN: That's correct. Among those with confirmed infections in this report, about 10 percent had a baby that was identified with one of these serious birth defects. However, there is a major gap we're seeing in evaluation of these infants. So while we recommend brain imaging after birth for every baby whose mother had Zika during pregnancy, based on the reports we've received, only about 1 in 4 of the babies are getting this imaging. So we might be underestimating how many are really impacted by Zika at this point.
SIEGEL: Zika spreads by mosquito, but it can also be spread through sexual contact. What can you tell us about how many cases have been spread, by what manner?
HONEIN: We think the vast majority of the transmission is occurring through mosquito bites. But both mosquito bites and sexual transmission is a risk, and prevention is really key here. Every week, 30 to 40 pregnant women with Zika are being reported to the U.S. Zika Pregnancy Registry, so preventing mosquito bites - insect repellent, long sleeves, long pants - and preventing sexual transmission through condoms or not having sex during pregnancy, these are really important to lower the risk of Zika.
SIEGEL: The weather is getting warmer. Mosquito season is about to start. What do you think we can expect to see here in the U.S. over the summer and beyond?
HONEIN: It's really not possible to predict what we are going to see in the U.S. If it's going to be a lot of transmission or a small amount of transmission, we just need to be ready to do everything we can to protect pregnant women and their babies from this really serious virus.
SIEGEL: That's Margaret Honein, head of the birth defects branch at the Centers for Disease Control and Prevention. Thank you very much for talking with us.
HONEIN: Thank you very much.
(SOUNDBITE OF PEOPLE UNDER THE STAIRS SONG, "ACID RAINDROPS") Transcript provided by NPR, Copyright NPR.