Over 150 pregnant women in the United States appear to have been infected with Zika virus. That's in addition to more than 120 women affected by Zika in U.S. territories, mainly Puerto Rico.
Those are the latest figures from the Centers for Disease Control and Prevention in Atlanta, which has been keeping track of all pregnant women in the U.S. and its territories who have lab tests suggestive of Zika virus infections.
So far, officials say they are aware of fewer than a dozen pregnancies that have had complications, although many of the pregnancies are ongoing. "We don't have full information yet on all of the outcomes," says Margaret Honein, chief of the CDC's birth defects branch.
Zika virus infection has been associated with miscarriage as well as birth defects like unusually small brains, called microcephaly. The exact risk posed by the virus remains unclear, and figuring that out is one reason the CDC is keeping track of affected pregnancies.
In the past, the CDC publicly reported on only those women who had both positive lab tests as well as symptoms. But officials say recent research suggests that women do not necessarily have to have symptoms to have their pregnancies affected. So the CDC is expanding its reporting to include women who didn't have symptoms.
"As the data accumulated about the risk of asymptomatic infections, it seemed more and more important to be very transparent and share publicly the numbers, the full number of pregnant women at risk of adverse outcomes associated with Zika," said Honein in a press briefing Friday.
Among the 157 pregnant women from U.S. states and the District of Columbia who are being monitored, only 49 percent reported symptoms consistent with Zika — mostly rash and fever.
Right now, CDC officials say they have no evidence that anyone has gotten Zika from being bitten by a mosquito in the continental United States. But public officials worry that this may eventually occur in places that have seen local transmission of other mosquito-borne disease, such as dengue.
ARI SHAPIRO, HOST:
Nearly 300 pregnant women in the U.S. and its territories have tested positive for a Zika virus infection. It sounds like a big jump in cases, but it's mostly because of a change in how the numbers are reported by the Centers for Disease Control and Prevention. NPR's Nell Greenfieldboyce explains.
NELL GREENFIELDBOYCE, BYLINE: It used to be that a pregnant woman would have to have more than just lab test results to get reported in the official CDC numbers. She'd also have to have symptoms of Zika, like rash or fever. But that's no longer the case. Margaret Honein is chief of the CDC's Birth Defects branch. She says the agency will now include all pregnant women with positive test results, even if they don't recall any symptoms. That's because there's growing evidence that an infected woman doesn't need feel sick for her pregnancy to be at risk.
MARGARET HONEIN: As the data accumulated about the risk of asymptomatic infections, it seemed more and more important to be very transparent and share publicly the full number of pregnant women at risk of adverse outcomes associated with Zika.
GREENFIELDBOYCE: She says so far, officials know of fewer than a dozen bad outcomes, like miscarriage or birth defects.
HONEIN: But we don't have full information yet on all of the outcomes.
GREENFIELDBOYCE: ...Because most of the pregnancies are ongoing. The CDC says it has no evidence that mosquitoes are spreading Zika in the continental United States. Here, the 157 pregnant women with Zika either had traveled to an affected region or had sex with a traveler.
Today top health officials briefed President Obama on the Zika situation. He spoke to reporters in the Oval Office and said work was underway on a vaccine and better diagnostics.
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BARACK OBAMA: We're also working with all the states so that they are properly prepared if we start seeing an outbreak here in the continental United States during the summer when, obviously, mosquitoes are more active.
GREENFIELDBOYCE: He said all that work costs money and urged Congress to fully fund his $1.9 billion request for Zika. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.