The Food and Drug Administration is recommending that blood banks screen all blood donations in the U.S. for the Zika virus.
It's a major expansion from a Feb. 16 advisory that limited such screening to areas with active Zika virus transmission.
In a statement released Friday, the FDA says all those areas are currently in compliance with blood screening, but that expanded testing is now needed.
"As new scientific and epidemiological information regarding Zika virus has become available, it's clear that additional precautionary measures are necessary," the FDA's acting chief scientist, Luciana Borio, said in the statement.
The expansion of testing won't happen all at once. The FDA is advising blood establishments in 11 states to begin testing within the next four weeks. Those states include Alabama, Arizona, California, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, South Carolina and Texas.
These states are in proximity to areas where Zika is actively spreading via mosquitoes or where there are a significant number of cases related to other exposures, including sexual transmission.
Within 12 weeks, blood facilities in all states should be testing donations for Zika, the FDA says.
Currently, Zika is being spread by mosquitoes in South Florida, Puerto Rico and the U.S. Virgin Islands, as well as most countries in the Caribbean and Central and South America. There are a total of 2,517 cases of Zika in the U.S. states and D.C., according to the Centers for Disease Control and Prevention, with 9,011 more in U.S. territories.
Most of the cases within the U.S. are related to travel abroad or sexual transmission. The cases in Puerto Rico and the U.S. Virgin Islands are a mix of travel-related cases and locally acquired infections via mosquitoes or sex.
In issuing the new recommendations, the agency noted that 4 out of 5 people infected with Zika virus never develop symptoms. Thus, questions that blood banks routinely ask about the risks of disease might not catch people who have been exposed and who have been infected with the Zika virus.
Zika virus infection during pregnancy has caused serious birth defects in a few cases in the U.S. and hundreds of cases in Central and South America where infants have been born with microcephaly, a condition where the brain and skull are malformed.
There have been no cases of Zika related to blood transfusions in the U.S., according to the Centers for Disease Control and Prevention.
"There is still much uncertainty regarding the nature and extent of Zika virus transmission," says Peter Marks, director of the FDA's Center for Biologics Evaluation and Research. "At this time, the recommendation for testing the entire blood supply will help ensure that safe blood is available for all individuals who might need transfusion."
In a news conference Friday, Marks said that there had been one case in Florida where a unit of donated blood was tested and taken out of the blood supply. Other units where Zika is suspected are currently under investigation, he said.
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. Transcript provided by NPR, Copyright NPR.