KELLY MCEVERS, HOST:
The Food and Drug Administration today dramatically expanded its recommendations for protecting the blood supply from the Zika virus. The FDA says all blood donated anywhere in the United States should be screened for Zika. NPR health correspondent Rob Stein is with us now to explain this development. Hey there, Rob.
ROB STEIN, BYLINE: Oh, hey - hey.
MCEVERS: So the FDA already had been recommending that some blood donations be screened for the Zika virus. Tell us a little more about what was already going on and what's new here.
STEIN: Yeah, you know, we've known for a while that Zika could be transmitted through a blood transfusion. And because of that, the FDA's been recommending that blood centers turn away anyone who recently traveled to a place where the virus is spreading. And the FDA has also been telling places where the virus is - they know it's spreading through mosquitoes, like Florida and Puerto Rico, that they should test all blood donors. And some other places have been doing it voluntarily just to be on the safe side, some of the southern states.
But what the FDA is now saying is that all blood that's donated anywhere, any part of the country, should be screened for the Zika virus. And we're talking about - you know, we're talking about a million units of blood every month.
MCEVERS: Why? I mean, what prompted the FDA to want such a huge expansion of the screening of blood for Zika?
STEIN: So the FDA is basically saying we've hit kind of a tipping point with Zika in the United States. You know, we now have - you know, at least a couple thousand travelers have come into the country infected with the virus. There's this huge outbreak that's going on right now in nearby Puerto Rico. And we have these small clusters of infections that are being spread by mosquitoes in Florida, in a couple of neighborhoods in Miami.
And so you know, there's a lot of concern that, you know, most people who have the Zika virus don't even know it. They have no symptoms. And we know the virus can be spread through sexual transmission. So there's a lot of concern that pregnant women could get infected through a blood transfusion or through sexual contact with somebody who got infected through a blood transfusion.
MCEVERS: Explain that a little bit more.
STEIN: So, you know, as I said, you know, the biggest risk for Zika is to pregnant women. That's the biggest concern is that we know that Zika can cause miscarriages when women get infected when they're pregnant. We know that it can cause this terrible birth defect called microcephaly. That's where babies are born with, you know, really small heads and sometimes severely damaged brains.
And so the concern is that that may only be the - kind of the tip of the iceberg. There's also concerns that even babies that are born that seem healthy are not OK. They might end up with other kinds of problems like blindness or deafness or developmental problems down the road. We just don't know with Zika because it's just so new.
MCEVERS: So has anyone gotten infected with Zika through a blood transfusion?
STEIN: So we know that there's been at least a couple of cases that have been documented in Brazil, where this all started. So far, we don't know of any cases in the United States where someone got infected through a blood transfusion, but there was at least one case in Florida where a blood donor did test positive for the virus. Now, that blood donation was discarded so it never made its way into the blood supply, but there are several other possible cases that are under investigation we don't know about yet. And we do know that in Puerto Rico, at least 1 percent of the blood donors have been testing positive for Zika.
MCEVERS: So quickly, how is all this testing of the blood going to work?
STEIN: So the FDA says that 11 states, the ones that are considered at highest risk, should start as soon as possible, within four weeks. And most of those states are in the South. You know, that makes sense. They're states that are where the mosquito that spreads the virus are most common, like Alabama, Arizona, Georgia, Louisiana, Mississippi, New Mexico and South Carolina and Texas. But there are a couple other states on that list - California and New York. That's because those are states where a lot of travelers that come in infected with the virus.
MCEVERS: That's NPR's health correspondent, Rob Stein. Thanks very much.
STEIN: Oh, sure, nice to be here.