Before the test for HIV was developed in March 1985, HIV was spread to people who received blood or blood products donated by HIV-infected people. Since 1985, the risk has been almost eliminated. Blood banks and health professionals:
Today, the risk of getting HIV from a transfusion of one unit of blood is extremely low. This low risk does not decrease the importance of limiting the use of donated blood or encouraging people who know they are going to have surgery to donate their own blood (autologous donation).
WebMD Medical Reference from Healthwise