EBV infection appears to be a necessary but not sufficient requirement for developing MS, EBV seroprevalence is higher among people with MS, symptomatic EBV infection (IM) is more prevalent among people with MS, and HLA-DRB1*1501 genotype modifies the effect of anti-EBV antibody titre on MS risk. This evidence concerns the gene HLA-DRB1 and Epstein-Barr virus infection.