Transfusion transmission of human prion diseases.

No transmission through transfusion has been reported for classic Creutzfeldt-Jakob disease (CJD). Moreover, a series of epidemiological surveillance, case-control, and look-back studies have provided no evidence of such transmission of CJD. Hence, the risk of such transfusion transmission of classic CJD remains theoretical. In contrast, based on data from the United Kingdom, the likelihood of transmission of the agent of the variant form of CJD (vCJD) through blood transfusion by donors who develop the disease within several years of donation is about 14% for recipients who survive longer than 5 years posttransfusion. Leukodepletion may reduce the likelihood of vCJD transmissions, although this procedure by itself removes less than half of the prion infectivity of blood. The potentially longer incubation periods of vCJD with infections in donors who are not methionine/methionine homozygous at codon 129 of the prion protein gene, the unknown number of such donors, and the unknown infectivity of their blood during the incubation period suggests caution in assuming that only known cases of vCJD represent a risk for the transfusion transmission of vCJD. Results from ongoing look-back investigations and other studies will enable continued monitoring and more precise estimations of the risks of the transfusion transmission of CJD and vCJD.