The FDA also advises blood banks to quarantine any blood identified as having come from SARS patients or people potentially exposed to SARS.
"FDA is taking this interim measure to assure the safety of the blood supply while more is learned about the disease," the agency said in a written statement Thursday. "At this time, it is unknown whether SARS can be transmitted through blood."
"It's a preventive measure," FDA spokeswoman Lenore Gelb told United Press International. "We don't even know if SARS can be transmitted in blood (but) even if there's a small chance, you don't want to wait until later and find out you're wrong," Gelb added.
Although there have been no cases of people contracting SARS via tainted blood, genes of the virus that cause the illness have been detected in the blood of patients so it is theoretically possible that it could be transmitted in blood, the FDA said.
Dr. Louis Katz, president of America's Blood Centers, told UPI the blood bank industry views the precautions as "appropriately cautious" given the uncertainty about whether the SARS virus can be transmitted via blood.
However, Katz added, "We hope to prove that it's not transmitted by blood. I think we will show that eventually."
The number of people infected with SARS rose by 72 Friday bringing worldwide total to 3,288 cases and 170 deaths, according to the World Health Organization. China and Hong Kong, now a Special Administrative Region of China, continue to be the two areas hardest hit by the disease with both reporting double-digit increases in new cases.
China reported 25 new cases, bringing its total to 1,482 people infected and 65 deaths. Hong Kong increased its number of cases by 30. So far, 1,327 people have become infected with SARS in Hong Kong and 69 have died from the illness.
Under the new FDA guidance, people who contracted SARS would be deferred from donating blood until 28 days after their symptoms had resolved.
People who have recently traveled to Asian regions where SARS is prevalent also would be barred from donating blood for 14 days after their return to the United States. These regions consist of China, Hong Kong, Hanoi, Vietnam and Singapore.
Katz said current screening procedures already bar ill people from donating so anybody with SARS symptoms should not have been allowed to give blood. However, the SARS virus could be in the blood of people who are not sick yet and that raises the possibility that recently infected people might have donated and the virus could have gotten into the blood supply, he said.
For this reason, the FDA guidance also calls for blood banks to encourage people who have already given blood to notify the center where they donated if they had SARS 28 days prior to the date they donated or had any potential exposure to SARS within 14 days before donation or developed SARS symptoms 14 days after donation.
Any blood "identified as having come from potentially SARS-exposed or infected donors will be quarantined and indefinitely kept out of the general blood supply," the FDA said.
Health officials are working to finalize a test for diagnosing people infected with the SARS virus. The research could also prove helpful in developing a test for detecting the virus in donated blood, Katz said.
A test for screening blood may not be necessary if it turns out the SARS virus is not transmitted via blood products, but if the test is needed "a lot of that work is in progress already," he said.
The FDA estimated the number of donors that would be deferred under this new guidance would be minor and would have little impact on the blood supply. "It is believed that 0.1 percent to 0.2 percent of potential donors, and at most 0.4 percent, will be deferred as a result of the guidance at this time," the agency said.
Katz agreed with that assessment, saying, "We think the number of people we're going to defer are relatively small (and) we don't expect to see any blood shortages because of this."
Blood banks have 30 days to implement the new screening procedures.