The Food and Drug Administration on Friday took steps to safeguard the nation’s blood supply from the Zika virus, calling for all blood banks to screen donations for the infection even in states where the virus is not circulating.
The recommendations are an acknowledgment that sexual transmission may facilitate the spread of Zika even in areas where mosquitoes carrying the virus are not present. Officials also want to prepare for the possibility that clusters of local infection will continue to pop up in parts of the United States for years to come.
“There could be multiple outbreaks of Zika happening outside the known current ones in South Florida, but because we are not actively looking they could be happening silently,” said Dr. Peter J. Hotez, the dean of the National School of Tropical Medicine at Baylor College of Medicine, who applauded the F.D.A.’s move.
Without federal funds, it is generally not possible for local health departments to conduct active surveillance for Zika virus in the blood or urine of patients with fever or rash, he added.
“In some ways the inaction from Congress has forced the F.D.A. to adopt this position,” Dr. Hotez added. “They have no other choice.”
The agency urged blood centers to use one of two experimental tests intended to detect active infections, called nucleic acid tests, before releasing donated blood for use in transfusions. As an alternative, banks may decontaminate plasma and platelets with so-called pathogen reduction technology.
But the recommendations are likely to pose a significant challenge for some blood banks and for the third-party labs that perform much of the blood screening nationwide, some experts said.
Eleven states must put the new safeguards into place within four weeks. They include Alabama, Arizona, California, Georgia, Louisiana, New York and Texas, which have many residents who travel to Zika-affected countries or are near an area that already has locally acquired mosquito-borne cases.
Other states have 12 weeks to carry out the recommendations.
“This is a bombshell, because this is extremely rapid introduction of a new test nationwide that’s almost unprecedented,” said Dr. Jeffrey McCullough, emeritus professor of laboratory medicine and pathology at the University of Minnesota Medical School. “To try to implement this, in four weeks, is really, really difficult.”
Yet the new safeguards also are necessary, Dr. McCullough said. Under current guidelines, it is too difficult to identify infected donors by “trying to sort out risky donors by history of where they’ve been or what they’ve exposed to.”
Nationwide, nearly 14 million units of whole blood and red blood cells are collected each year from about seven million donors. Every day, as many as 36,000 units of red blood cells are given to patients, along with 7,000 platelet units and 10,000 units of plasma. Consistent screening of the blood supply is an enormous task.
There are more than 11,500 confirmed cases of Zika virus in states and territories, according to the C.D.C. Nearly 2,500 of them are people in the continental United States who traveled abroad where Zika-infected mosquitoes are circulating. More than 30 cases were acquired in Florida.
Puerto Rico has been screening all blood donations since March. TheCenters for Disease Control and Prevention in June found that asurprisingly high percentage of donors had signs of active infection with the Zika virus.
The F.D.A. provisionally approved two screening tests for Zika in blood donations on an investigational basis in March and June respectively. The first is made by Roche Molecular Systems, and the second by a collaboration between Hologic Inc. and Grifols.
Neither test is fully F.D.A approved yet, and the facilities using them are enrolled in a continuing study. As part of Roche’s investigation, four centralized testing labs that screen blood for multiple banks in the South have been “collecting and testing blood for weeks now,” said Tony Hardiman, who leads the blood screening operations at Roche.
For the 11 states that need to be ready in a month, he said, “we are pretty much locked and loaded.”
“Our focus now is what do we do for the rest of the country to bring them up in 12 weeks,” he added.
Officials at Blood Systems, which operates blood banks in 24 states, said they will be able to test blood donations in California and some Southern states like Mississippi in a month. The company will then work on getting sites in the Rocky Mountain States operational, said Dr. Ralph R. Vassallo Jr., the chief medical and scientific officer.
Creative Testing Solutions, a large blood donor testing lab, already is using both experimental Zika screening tests. In Tampa, the company has relied on Roche’s test since the Zika outbreaks began in Miami-Dade County.
In its Dallas and Phoenix outposts, C.T.S. has installed two so-called Panther machines to be able to screen tubes of blood with the Hologic-Grifols test, in case Zika-infected mosquitoes arrive along the Gulf Coast.
In light of Friday’s F.D.A. recommendations, officials said they will have to train more employees to use new tests and significantly scale up.
“We test 35 percent of the blood supply, so in order to be able to do that in all states in 12 weeks, we are going to need additional pieces of equipment,” said Marc Pearce, a spokesman for C.T.S. — 12 more Panthers and one more machine that runs the Roche test.
Asked on a conference call with reporters about funding the new safeguards, Dr. Peter Marks, the director of the F.D.A.’s Center for Biologics Evaluation and Research, said, “I can’t speak to the cost of implementation at this time.”
Hospitals may wind up paying more for each unit of blood because of additional screening costs, some experts said.
“When hospitals hear this, they will be concerned that they could see a cost increase of up to $8 more per unit,” Dr. Vassallo said, which is roughly how much it costs to screen each unit for the Zika contamination.
This month, after the first cases of local transmission in Miami were discovered, some blood banks near Zika hot zones in Florida began screening blood donations. According to Dr. Marks, one donation contaminated with the virus had been found in recent weeks in the state.
The bag of contaminated blood was discarded. “The system worked correctly,” Dr. Marks said.