Stronger evidence for connection between Epstein-Barr virus and multiple sclerosis

A new analysis of data from U.S. military recruits suggests multiple sclerosis (MS) – a disease considered of unknown etiology – is a complication of infection with Epstein-Barr virus (EBV). Multiple sclerosis is a chronic demyelinating disease of the central nervous system. The underlying cause of this disease is not known, but Epstein-Barr virus is thought to be a possible culprit. However, most people infected with this common virus do not develop multiple sclerosis, and it is not feasible to directly demonstrate causation of this disease in humans. Using data from more than ten million United States military recruits monitored over a 20-year period, 955 of whom were diagnosed with MS during their service, Kjetil Bjornevik et al. tested the hypothesis that MS is caused by EBV. They found that the risk of developing MS in individuals who were EBV-negative increased by 32-fold following EBV infection. "These findings," say the authors, "cannot be explained by any known risk factor and suggest EBV as the leading cause of MS." They note that one of the most effective treatments for MS is anti-CD20 monoclonal antibodies. Directly targeting EBV could have major advantages compared with anti-CD20-based therapies, they say, which have to be administered by intravenous infusion and may increase the risk of infections. A related Perspective discusses these findings in more detail.