• blood transfusion;
  • residual risk of infection;
  • HIV;
  • HBV;
  • HCV

Summary. We conducted a retrospective cohort study to estimate the incidence of major blood-borne agents among Italian blood donors and calculated the risk of infection among blood recipients using the ‘incidence/window period model’. The study was conducted among 46 180 blood donors enrolled in six blood centres between 1994 and 1999. During follow-up, seven new infections were confirmed: three donors seroconverted for anti-human immunodeficiency virus (HIV); two for anti-hepatitis C virus (HCV); and two showed hepatitis B surface antigen (HBsAg) reactivity; no cases of syphilis were observed. The incidence rates per 100 000 person/years were: 4·06 (95% CI: 0·82–11·85) for HIV; 2·41 (95% CI: 0·29–8·70) for HCV; and 2·70 (95% CI: 0·32–9·77) for HBsAg; the incidence for total hepatitis B virus (HBV) infection was 9·77 per 100 000 person/years (95% CI: 1·16–35·36). The estimated risk of an infectious blood unit not being detected was: 2·45 (95% CI: 0·13–12·33) per 1 million units for HIV; 4·35 (95% CI: 0·30–22·39) for HCV; and 15·78 (95% CI: 1·16–84·23) for HBV. Overall, an estimated 22·58 per 1 million units are infected. In Italy, the risk of transfusion-transmitted infections is low and is similar to that in other western countries. The introduction of new more sensitive screening tests could reduce the residual risk of transfusion-transmitted infection by 40–80%.