Current viral risks of blood and blood products.

A number of viruses may be transmitted by blood transfusion, the most important of these are HIV, human T-cell lymphotrophic retrovirus (HTLV), hepatitis B virus (HBV), and hepatitis C virus (HCV). A series of overlapping safety measures are in place and are being improved and supplemented continuously. As a result, the risk of transmission of these viruses in the USA has been reduced to between one and four per million blood components transfused.