Epidemiology of variant CJD.

There are 100 confirmed cases of variant CJD (vCJD) in the U.K., with four cases in other countries (France and the Republic of Ireland). In the U.K., The mean age of onset is 28 years (range 12-74) with a median duration of 13 months (range 6-39). There are reported regional variations in incidence in the U.K., with a North/South difference and a 'cluster' of cases in one county, Leicestershire. The incidence of cases in the U.K. is rising. There are concerns about the possibility of secondary, iatrogenic, spread of vCJD, especially given the finding of positive PrP immunocytochemistry in lymphoreticular tissue. Experimental evidence has confirmed the presence of infectivity in blood in transmissible spongiform encephalopathy (TSE) models, but the significance of this in relation to human blood practice is uncertain. The accumulated epidemiological evidence has not shown blood to be a risk factor for sporadic CJD, but variant CJD may behave differently. A Transfusion Medicine Epidemiological Review in the U.K. is collecting data on CJD case donors and recipients, with negative results to date.