Earlier this month, a longitudinal analysis of over ten million adults in the US military revealed that the Epstein-Barr virus (EBV) was associated with a 32-fold increased risk of developing multiple sclerosis (MS). Moreover, the paper published in Science by Bjornevik and colleagues goes beyond assessing the association between EBV infection and MS by suggesting that EBV may be the leading cause of MS, and has consequently garnered significant attention. These results, if true, indicate that efforts to prevent EBV infection may reciprocate to MS, which could have a substantial effect on the epidemiology of MS.
Often recognised for its role in mononucleosis, EBV has also been shown to increase the risk of MS, but had not previously been studied enough to identify its role in causing MS. The longitudinal analysis by Bjornevik and colleagues was conducted from a representative cohort of over ten million individuals over a 20-year period. The study rules out potential confounding and reverse causation (where EBV is a consequence of MS and not vice versa) and thus presents the most substantial evidence of EBV’s causal role in the development of MS. Given that EBV is a highly transmissible virus that impacts an estimated 90% of individuals worldwide, and many of these individuals do not know that they are infected, efforts to prevent EBV are underscored by this study.
Unfortunately, according to the Mayo Clinic, EBV infection generally only results in mononucleosis symptoms in about 25% of teenagers and young adults. As a result, preventing transmission by isolating symptomatic cases has little effectiveness, and thus new strategies to prevent EBV seroconversion are necessary and underway, such as through the development of vaccines and antiviral treatments.
If EBV is indeed a causative factor for MS as suggested by this analysis, depending on their effectiveness, these developments could greatly reduce MS incidences by reducing the number of people at an elevated risk of developing MS. In turn, a sharp reduction in incidences could also lower the number of lifetime diagnosed prevalent cases of MS in the future, which, according to GlobalData, is expected to increase to over 1.59 million in the seven major markets by 2028 (as shown in Figure 1). Such a reduction would be a welcome sign, as MS can profoundly negatively impact the quality of life for those with the chronic inflammatory demyelinating disease.