Reduction in the risk of transmission of the 4 most frequently transmitted, potentially fatal, transfusion-acquired infections in the United States since the mid-1980s. The figures plotted pertain to risk reduction documented between 2001 and 2004 (for bacteria in platelets), 1992 and 2001 (for HBV), and 1984 and 2001 (for HCV and HIV). The risk of bacteria in platelets today is considered to be the same as in 2004, and the risk of HBV, HCV, and HIV the same as in 2001, because no further measures to protect the blood supply from these pathogens have been introduced since the latest risk estimates⁶¹  were published. The depicted risk estimates reflect the approximate per-unit risk based on various sources (recipient follow-up studies, donor prevalence studies, or mathematical models of the risk of transmission).⁷  There are no published US data on the risk of bacterial contamination of platelets after several measures (bacterial detection, substitution of single-donor platelets for pools of 4 to 6 whole blood–derived platelets, and/or various process improvements to reduce risk) were implemented in or around 2004. Based on other available literature reviewed in the text in the “TAS” subsection,^78-80  the depicted risk reduction represents the authors' estimate of the effect of these combined approaches.