 Genetic testing of the 16 positive samples revealed a higher proportion of valine homozygous (VV) genotype on the codon 129 of the gene encoding the prion protein (PRNP) compared with the general UK population.This also differs from the 176 people with vCJD, all of whom to date have been methionine homozygous (MM) genotype.The concern is that individuals with this VV genotype may be susceptible to developing the condition over longer incubation periods.