Transfusion‐transmitted emerging infectious diseases: 30 years of challenges and progress

The introduction of blood donation screening for syphilis in the 1940s, followed by hepatitis B surface antigen (HBsAg) testing in the early 1970s and the subsequent conversion in the United States to an all-volunteer blood supply led most to believe that, with the exception of residual posttransfusion non-A, non-B hepatitis, the blood supply was relatively safe and would remain so for the foreseeable future. However, with the recognition of AIDS/human immunodeficiency virus (HIV) as a worldwide threat to the safety of the blood supply in 1982 to 1983, times of complacency were over and there was a critical need to increase vigilance and decrease the response time to threats to recipient safety. Even before the current proactive focus on emerging infectious disease (EID) agents, the blood industry’s progressive response to HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) was noteworthy. Our responses to established and EID agents transmissible by labile blood components continue to be based on two main interventions: donor selection and questioning, to remove those with recognized risk factors, and testing to deal with what remains. It is important to recognize that the earliest “firstgeneration” tests for HBsAg, viral lysate-based HIV antibody and single-antigen HCV antibody tests, albeit less than optimal in sensitivity and specificity, successfully removed more than 90% of the pretesting risk within 1 to 2 years of discovery of the etiologic agents. Subsequent development of secondand third-generation assays achieved our current expectations of test sensitivity of more than 99.9%. The public expects an absence of infectious disease transmissions, most notably for highly infectious and pathogenic agents like HIV. Thus, we must recognize and acknowledge the contributions of the test manufacturing industry, which have enabled the incredible gains in blood supply safety achieved over the past three decades. As an example, Figures 1A and 1B display the enormous effort and investment that industry has provided to the transfusion community with the release worldwide of more than 50 versions of HIV serologic assays since 1985. Together with nucleic acid testing (NAT) in the United States and most of the industrialized world, HIV residual risks (along with those of HBV and HCV) are currently estimated at less than 1 per million transfused units. Plasma-derived products have had the additional benefit of pathogen reduction, which in combination with the other two interventions, has nearly eliminated infectious disease risks of plasma derivatives. In August 2009, a group from the AABB Transfusion Transmitted Diseases (TTD) committee published a supplement to TRANSFUSION (see also http://www .aabb.org/resources/bct/eid/Pages/default.aspx) that reviewed the definition and background of EID agents that pose a real or theoretical threat to transfusion safety, but for which an existing effective intervention is lacking. Emergence was recognized as due to multiple factors, ABBREVIATIONS: B19V = human parvovirus B19; CHIKV = chikungunya virus; CoV(s) = coronavirus(-es); DENV = dengue viruses; ECDC = European Centres for Disease Control; EID(s) = emerging infectious disease(s); MERS = Middle Eastern respiratory syndrome; PARV4 = parvovirus 4; SARS = severe acute respiratory syndrome; vCJD = variant Creutzfeldt-Jakob disease; WNV = West Nile virus.