Risks of transmission of variant Creutzfeldt-Jakob disease by blood transfusion.

Variant Creutzfeldt-Jakob disease (vCJD) was first identified in 1996 in the UK, and results from human exposure to the bovine spongiform encephalopathy (BSE) agent. vCJD has subsequently been identified in 10 additional countries, and numbers continue to increase in the UK. Unlike other human prion diseases, infectivity and the disease-associated form of the prion protein are readily detected in lymphoid tissues in vCJD. In experimental BSE infection in a sheep model, infectivity has been transmitted by blood transfusion from asymptomatic infected animals to normal recipient animals, indicating that infectivity is present in blood during the incubation period. Recently, two cases of apparent iatrogenic vCJD infection by blood transfusion from asymptomatic donors who subsequently died from vCJD have been reported from the UK. The first case resulted in clinical illness identical to other cases of vCJD, while the second case was an asymptomatic infection detected at autopsy. Sensitive means of detection of disease-associated prion protein in the blood are required in order to be employed for screening purposes, both individually at the time of blood donation, and to help ascertain future numbers of vCJD cases in the UK and beyond.