Based on the revised guidelines, cases with high-virulent STEC infection are determined by microbiological and clinical information and are those: (i) positive for stx2 subtypes 2a, 2c, 2d, or (ii) positive for stx1 subtype 1a in a patient ⩽5 years with bloody diarrhoea, or (iii) notified as a HUS-patient, or (iv) negative for stx, but eae-positive E. coli strain (STEC-LST) with a genotype previously seen in a HUS case. This evidence concerns the gene STX2 and hemolytic-uremic syndrome.