It was the first time the agency had disclosed the number of Zika-infected pregnant women in the U.S. and its territories.
U.S. health officials have previously said that the virus, which is spread through mosquitos and sexual contact, can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.
The Centers for Disease Control and Prevention said Friday that it is monitoring 279 pregnant women with likely Zika virus infections across U.S. states and territories. The largest number of cases by far are in Puerto Rico, where officials are keeping tabs on 122 pregnant women. But they also are tracking 157 other pregnant women across the country.
“One challenge of this Zika virus outbreak is the lack of understanding of the magnitude of risk and the spectrum of outcomes associated with Zika virus infection during pregnancy,” researchers wrote in a report published Friday. The surveillance effort, they noted, is expected to change that, “enhance risk assessment and counseling of pregnant women and families, advance clinical care, and assist states and territories to anticipate and plan needed resources and increase prevention efforts.”
The report does not detail the outcomes of any pregnancies currently being monitored but says that information “will be shared in future reports.” Researchers said the agency will begin posting a weekly update on the number of cases being watched.
President Obama is scheduled to receive an Oval Office briefing late Friday morning about the country’s Zika planning from CDC director Tom Frieden, Health and Human Services Secretary Sylvia Burwell and Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
Friday’s news also comes amid the latest push in Congress for more resources to prepare for and combat the spread of Zika domestically. On Thursday, the Senate approved $1.1 billion in emergency funding, substantially more than the $622 million funding package the House approved a day earlier — in part by using money set aside for Ebola.
The White House, which in February requested $1.9 billion for its Zika response, called the House’s measure “woefully inadequate.”
As of this week, the United States had 544 reported cases of Zika, nearly all of them involving people who had traveled to countries already plagued by the virus. A handful of infections have been sexually transmitted, but none has yet been acquired from mosquitoes in this country. In addition, there have been more than 800 Zika cases in U.S. territories, the vast majority of those in Puerto Rico, where local transmissions through mosquitoes have been common.