The effort to clean the nation's blood banks of the AIDS virus has apparently been successful, with screening programs spotting virtually all blood donors suspected of having contact with the virus, according to leaders at three key federal health agencies.
Recipients of blood transfusions run little risk of being infected with the AIDS virus because of the success of screening programs as well as the voluntary self-exclusion from blood donations by members of high-risk groups, said officials of the federal Centers for Disease Control, the Food and Drug Administration and the National Institutes of Health.
In a major review of the safety of the national blood system, the officials said they believe that virtually all donors with suspect blood are being identified and their blood eliminated from the system.
So far, 202 cases of acquired immune deficiency syndrome were reported to have been received through blood transfusions and 82 cases were contracted by hemophiliacs who probably got the disease through the blood-bank product called Factor VIII. Now, in addition to identifying suspect donor blood, a heat-treatment procedure in manufacturing plasma products such as Factor VIII has all but eliminated the virus in those blood products as well.
The huge screening program, which tested 1.1 million units of blood, has uncovered results that indicated the presence of antibodiesagainst the AIDS virus in about one out of 400 donors.
According to Dr. Harry M. Meyer, director of the FDA Center for Drugs and Biologics, "This is evidence that for making the blood supply safer, the test is extremely accurate" because it fits well with predictions based on tests with smaller samples.
Not all of the positive samples mean that their donors have AIDS -- only that they may have had the virus or something like it sometime in their lives. More elaborate, secondary tests are done on the samples, and about one third of the samples continue to be positive. Of these, the actual AIDS virus can be isolated in 60 percent of cases.
Of these final positive donors, only a fraction -- the experts would not say how many -- might be expected to develop the full syndrome. Others might develop Aids Related Cluster (ARC) with milder, flu-like symptoms, and some might harbor the virus without ever developing symptoms. These people, an FDA spokesman said, might continue to be carriers much the way some people carry the hepatitis virus.
Meyer said after the session that AIDS experts knew from tests among homosexuals, who account for about 73 percent of AIDS cases, that true positives -- people in whom the antibodies were truly identified -- probably "are harboring or carrying the virus somewhere in their bodies."
At the all-day meeting on the campus of the National Institutes of Health in Bethesda yesterday, Dr. James Curran, chief of the AIDS task force at the CDC, said that "despite our success, because of the long incubation period for AIDS -- up to five years or perhaps longer -- there will continue to be cases from blood transfusions , but mostly from persons who received their transfusions prior to implementation of the blood test."
According to Curran, the newest AIDS figures, as of July 26, show 12,067 cases, with 6,079 deaths.