Federal health officials say the number of women in the United States with the Zika virus has more than doubled, due to a change in the way the cases are counted.
The Centers for Disease Control (CDC) reported Friday there are now 157 women infected with the virus in 50 U.S. states and the District of Columbia and 122 cases in U.S. territories - mostly in Puerto Rico.
The latest numbers represent a significant increase from last week, when the CDC reported 113 women in all U.S. states and D.C. and 65 in U.S. territories.
Officials are now counting all pregnant women who test positive in the U.S. and its territories, whether or not they show symptoms. Previously, only pregnant women who had positive blood tests and Zika symptoms were counted.
The CDC said it changed its counting method out of concern that one type of blood test could produce false positive results if women were infected with a similar virus.
U.S. health experts have determined that the mosquito-borne virus can cause microcephaly, a birth defect that can result in severe brain abnormalities and developmental problems in babies.
The CDC said it dramatically ramped up its capacity to test for the Zika virus in preparation for the summer mosquito season.
This is the first time the agency had disclosed the number of infected pregnant women in the U.S. and and its territories.
In Washington, President Barack Obama received a briefing on Zika from members of his public health team.
“We don’t know all of the potential effects; we do know they are serious. Right now what we have seen is a little over 500 cases of Zika in the continental United States and they all appear to be travel-related, not mosquito transmitted,” Obama said.
He also urged Congress to pass a bill to increase emergency funding to tackle Zika.
“Congress needs to get me a bill. It needs to get me a bill that has the sufficient funds to get me a job,” Obama said, adding that Zika " is not something where we can build a wall to prevent—mosquitoes don’t go through customs.”