No SNVs reached genome-wide significance among participants with at least one DRB3 or DRB4 gene only, suggesting that the HLA-DR51 haplotype in combination with variants in the HLA-DRB1/5 intergenic region may singularly drive genetic risk for CDI in the European ancestry population. The gene discussed is HLA-DRB1; the disease is clostridium difficile infection.