Univariate analysis showed that the following covariates affected neurologic involvement onset in STEC-HUS: Leukocyte count (HR 2.719, 95%CI 1.478–5.000, p < 0.001), C-reactive protein (HR 1.686, 95%CI 1.011–2.811, p = 0.045), Hyponatremia (HR 2.227, 95% 1.276–3.888, p = 0.005) and C3 serum levels (HR 7.75, 95%CI 2.331–25.796, p < 0.001). This evidence concerns the gene C3 and Hyponatremia.