In the UK in the 1990s, there was an outbreak of the brain disease vCJD, which was caused by eating beef from cattle infected with the disease BSE. The type of meat thought to be infected was taken out of the food chain in 1989, and cases of vCJD have been declining since 2000. Susceptibility to vCJD is associated with two variants in a gene: M and V. We can inherit three possible combinations: MM, MV and VV. Until last year, all 177 people diagnosed with the disease in the UK had the MM combination. Recently, someone who had the MV combination has died of the disease. In the UK, 38% of people have the MM combination and 51% have the MV combination.