The Epstein-Barr virus (EBV) — best known for causing mononucleosis — also increases the risks for some people of developing seven other major diseases, according to a new study. The diseases are: systemic lupus erythematosus, multiple sclerosis, rheumatoid arthritis, juvenile idiopathic arthritis, inflammatory bowel disease, celiac disease, and type 1 diabetes. Combined, these diseases affect nearly 8 million people in the US.