-There was a significant difference between patients with T1D and healthy controls in the presence of anti-EBV IgM.-Nearly 43% of patients with T1D had anti-EBV IgG, unlike healthy individuals who did not.-The viral genome was present in 15 of 56 patients with T1D, while in the control group the genome was not detected. This evidence concerns the gene CD40LG and type 1 diabetes mellitus.