WHO Guidelines on Tissue infectivity distribution in Transmissible Spongiform Encephalopathies

Overview

Since first reported in 1996, up to June 2006, 161 cases of vCJD have occurred in the United Kingdom, 17 in France, four in Ireland, two cases in USA and the Netherlands and single cases in Canada, Italy, Japan, Portugal, Saudi Arabia and Spain. Cases of BSE and vCJD have been decreasing in the United Kingdom in recent years, but both diseases have appeared in other countries.

Until recently, all vCJD cases were attributed to consumption of beef products contaminated with the infectious agent of BSE. Since December 2003, three individuals have been identified with vCJD infections probably acquired from blood transfusions – two with typical vCJD symptoms and the other with pre-clinical vCJD involving spleen and lymph nodes but not brain. The fact that the three vCJD infections followed transfusions from clinically healthy persons who became ill more than a year after donating blood implies that other blood donors who might currently be incubating the disease would also be potential sources of infection for recipients. The possible extent of future blood-borne spread of vCJD infections is still unknown. The identification of these cases has intensifi ed the concern about possible unmapped ways in which the disease might spread. Except for the three transfusion-transmitted infections, no cases of vCJD have been linked to any medicinal product to date, and guidelines have been developed by the World Health Organization (WHO) and other authorities to minimize the risk.