Although the evaluation of SG8_31A and SG8_31B strains was difficult because such strains available for this study were very limited, these results indicate that infection by SG8_30 strains (all strains contain γ Stx2a phages and showed higher Stx2 levels) is associated with a higher risk of severe disease development among clade 8 infections; conversely, infection by SG8_32 strains (all contain δ Stx2a phages and showed lower Stx2 levels) is associated with a lower risk of severe disease. The gene discussed is STX2; the disease is infection.