The risk of transmitting prion disease by blood or plasma products.

Various experimental studies have shown infectivity in blood in relation to bovine spongiform encephalitis (BSE) and variant Creutzfeldt-Jakob disease (vCJD). Human to human transmission vCJD infection has been reported via transfusion of non-leukocyte-reduced red cells and, probably, via factor VIII concentrates. A number of precautionary measures are in place but uncertainties remain, especially concerning the number of BSE-infected people in the population. Additional measures such as prion filtration need consideration.