The risk of MS after infectious mononucleosis: meta-analysis

Vaccination against Epstein-Barr virus or EBV exposure during childhood may prevent many MS cases, according to authors of a recent meta-analysis showing infectious mononucleosis in adolescents and young adults to be a risk factor for MS.The authors note that Epstein-Barr virus (EBV) has been considered a cause of MS for the last 25 years due to the similarities in the epidemiology of infectious mononucleosis (IM) and MS. They explain, "Both IM and MS occur in young adults, both follow a latitude gradient, and both are rare in populations were infections occur at an early age, suggesting that late infection with EBV, evidenced by occurrence of IM, is an important causal factor in MS." Despite the epidemiological evidence linking IM and MS, studies evaluating MS risk in subjects with a history of IM have produced inconsistent results, leading the authors to conduct a meta-analysis of case-control and cohort studies to determine any association. Data from 14 studies (11 case-control studies and 3 cohort studies) provided odds ratios or risk ratios ranging from 0.8 to 17, with a median of 2.5, and meta-analysis produced a combined relative risk of 2.3 (95% CI, 1.7-3.0; pThe authors conclude that the results of the meta-analysis combined with results from serological investigations suggest the risk for MS increases after infection. They note, "Replication of the positive association between IM and MS in many studies suggests that the association is not a product of chance."Using their results and those of other studies, the authors provide a schematic representation of MS incidence according to the age of EBV infection. It illustrates a risk for MS close to zero among individuals who are not infected with the virus, an intermediate risk among individuals infected in early childhood, and a much higher risk in individuals first infected with the virus in adolescence or later in life. The authors say, "This model predicts that many cases of MS could be prevented by a suitable vaccine that protects against EBV." They add that many cases may also be prevented by exposing children to EBV infection early in life. Reference...