Previously, the U.S. Food and Drug Administration (FDA) had recommended that blood be tested for Zika in areas where there is active spread of the virus among mosquitoes. Now, all states are asked to test their donated blood for the virus, according to an announcement by the FDA Friday morning.

“There is still much uncertainty regarding the nature and extent of Zika virus transmission,” said Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research in a statement about the announcement. “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.”

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The FDA said it is making this recommendation after considering the latest science and consulting with public health experts. The agency also took into consideration the severe health problems that blood infected with Zika could cause pregnant women and their children if they are exposed while pregnant.

“Testing of donated blood is already underway in Florida and Puerto Rico, as well as in other areas, and it has shown to be beneficial in identifying donations infected with Zika virus,” the FDA said in a statement. “Expanded testing will continue to reduce the risk for transmission of Zika virus through the U.S. blood supply and will be in effect until the risk of transfusion transmission of Zika virus is reduced.”

Read more about the FDA’s announcement here.

This article previously appeared on Time.com.