Viral contamination of blood components and approaches for reduction of infectivity.

Currently, the United States blood supply offers a relatively low risk of viral infection. This is a result of careful selection of donors and extensive laboratory testing using sensitive procedures. Epidemiologic data show that there is some room for improvement in donor selection, but such improvements cannot be expected to entirely eliminate the collection of blood from infectious donors. Similarly, increased numbers of tests, along with improvements in the analytic sensitivity of these tests, may further reduce risk, but again, complete safety cannot be assured. Consequently, there is continuing interest in the development of safe and effective procedures for viral inactivation of single donor blood components. In order to establish appropriate expectations for such inactivation procedures, it is necessary to understand the titers and distributions of viral contaminants in blood components. Viruses may variously occur free in the plasma, as replicative forms in actively infected leukocytes, as integrated proviral DNA and perhaps, nonspecifically associated with cellular surfaces.