These findings have been reinforced by an extensive control study to identify risk factors for variant CJD, which recently identified two cases of human-to-human transmission of variant CJD infection through transfusions of particular types of red blood cells. These cases are particularly interesting, because the first case resulted in the clinical onset of variant CJD (with typical symptoms and pathology) 6.5 years after the transfusion from a donor who, although asymptomatic at the time of donation, subsequently developed and died from CJD.