MCALLEN, TX - APRIL 14:  A city environmental health worker displays literature to be distrubuted to the public on April 14, 2016 in McAllen, Texas. Health departments, especially in areas along the Texas-Mexico border, are preparing for the expected arrival of the Zika Virus, carried by the aegypti mosquito, which is endemic to the region. The U.S. Centers for Disease Control (CDC), announced this week that Zika is the definitive cause of birth defects seen in Brazil and other countries affected by the outbreak.  (Photo by John Moore/Getty Images)
PHOTO: John Moore/Getty Images
MCALLEN, TX - APRIL 14: A city environmental health worker displays literature to be distrubuted to the public on April 14, 2016 in McAllen, Texas. Health departments, especially in areas along the Texas-Mexico border, are preparing for the expected arrival of the Zika Virus, carried by the aegypti mosquito, which is endemic to the region. The U.S. Centers for Disease Control (CDC), announced this week that Zika is the definitive cause of birth defects seen in Brazil and other countries affected by the outbreak. (Photo by John Moore/Getty Images)
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Story highlights

The recommendation applies "across the board to anyone collecting blood"

Screening donated blood is already underway in Florida and Puerto Rico

(CNN) —  

The Food and Drug Administration has recommended screening the entire US blood supply for the Zika virus, it announced today, noting that screening donated blood is already underway in Florida and Puerto Rico.

The new recommendation applies “across the board to anyone collecting blood,” explained Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research. This includes very large blood collection establishments, such as the American Red Cross, and some very small establishments, such as academic centers, he said.

The Red Cross said it will phase in universal testing. Currently, it is conducting Zika tests in five southeastern states and will expand testing to four additional states in the south central and southwestern US over the next two weeks, the organization said in a statement. The Red Cross did not offer details about which states are covered.

Expanded testing should remain in effect until the risk of transmitting the virus through blood transfusions is reduced, the FDA recommended.

“We’ve come to a critical juncture: the risk to the blood supply combined with the uncertainty about the nature and extent of Zika virus transmission,” Marks said. More than 40 cases of mosquito-transmitted infection have been reported in South Florida.

Though the Red Cross does not collect blood in South Florida, as of August 1, Red Cross centers across the nation stopped accepting donations from people who have traveled to Miami-Dade County during the previous four weeks.

Though scientists are still learning about the virus, they know that Zika is transmitted primarily by mosquitoes but can also be spread by sexual contact. For pregnant women, an infection could cause microcephaly, a serious birth defect.

“About 80% of people who have Zika may never have symptoms,” Marks said. Symptoms can include fever, joint pain, rash and red, irritated eyes.

Because an infection could be transmitted during sex, someone who does not have symptoms might spread the virus to an individual who then donates blood, and this could lead to an “amplification” of the crisis, explained Marks.

The FDA issued its first Zika virus blood screening recommendation in February for areas with active transmission. At that time, the agency advised screening blood and blood components for the virus or stopping blood collection completely in areas of active transmission.

The nation’s first local, non-travel-related infection of Zika virus occurred in Puerto Rico in December. Shortly after, American Samoa and the US Virgin Islands reported similar locally transmitted infections. In July, Florida’s Miami-Dade County reported its own first case of a local mosquito-transmitted Zika infection.

With no FDA-licensed tests available for Zika, two experimental tests are being used to screen blood collected in the United States and Puerto Rico. Roche Molecular Systems’ Cobas Zika test became available in April, and Hologic Inc.’s Procleix test was put to use for Zika screening in June.

Both tests are considered “investigational,” meaning they’ve been scrutinized by the FDA but have not yet passed all of its usual requirements. “We carefully reviewed the information from the companies,” Marks said, “and we feel confident enough that we were able to make this recommendation.”

“The Cobas Zika test is a blood-screening test for blood donations only,” Roche spokesman Bob Purcell said. He said the test’s accuracy meets the expectations set out by the FDA.

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Procleix, the zika screening test from Hologic and a partner company, has been used by the American Red Cross to screen blood for HIV and hepatitis B and C.