From the initial discovery of variant Creutzfeldt-Jacob disease (vCJD) in the United Kingdom a decade ago, there has been concern about the ultimate extent and magnitude of the epidemic.1 Early estimates varied widely, with one model predicting up to 136 000 cases.2 Fortunately, the magnitude of the epidemic at present seems to match the lower limit of the early estimates, with 161 definite or probable cases in the United Kingdom. However, the article by Ironside and colleagues on p 1186 may rekindle fears that a larger epidemic is an ongoing threat.3

The study reports a genotype analysis that identified the presence of the homozygous valine (VV) genotype in two samples of appendix tissue that harboured prion proteins. The implication of this finding of most concern is that it raises the possibility that ongoing iatrogenic transmission of vCJD may sustain the epidemic.

Why are the …