Emerging pathogens in transfusion medicine.

Although the risk of infection with hepatitis and human immunodeficiency viruses from blood transfusions has been reduced to negligible levels, emerging infections continue to offer threats. Such threats occur with any infection that has an asymptomatic, blood-borne phase. In the past, it was thought that any emerging transfusion-transmitted disease would have epidemiologic properties similar to those of AIDS or viral hepatitis. Over the past 20 years, however, greatest concern has arisen from variant Creutzfeldt-Jakob disease, West Nile virus, and Babesia. These and other emerging infections are discussed in the context of blood safety.