NEW YORK (Reuters Health) Mar 28 - Infection with Epstein-Barr virus (EBV), manifesting as infectious mononucleosis, in adolescents and young adults, more than doubles the risk of developing multiple sclerosis (MS) later in life, results of a meta-analysis suggest.

"Multiple sclerosis is a complicated disease, probably caused by a combination of factors," lead author Evan L. Thacker from the Harvard School of Public Health, Boston, told Reuters Health. "It is likely that some viral infections, such as infectious mono, play a role in determining whether multiple sclerosis will occur."

Similarities in the epidemiology of infectious mononucleosis and MS have led researchers to consider EBV in the cause of MS, Mr. Thacker and two colleagues from Harvard point out in the Annals of Neurology for March.

"Both infectious mononucleosis and MS occur in young adults, both follow a latitude gradient, and both are rare in populations where infections occur at an early age, suggesting that late infection with EBV, evidenced by occurrence of infectious mononucleosis, is an important causal factor in MS," they explain.

However, studies that have evaluated the relation of infectious mononucleosis and MS risk have produced inconsistent results.

Against this backdrop, the Harvard group systematically identified and statistically combined 14 relevant studies conducted in the US, Europe, and Australia to come up with an overall picture of the connection between infectious mono and MS.

The combined relative risk of MS after infectious mononucleosis was 2.3, they report.

"The most important observation in our study was that people who got infectious mono while growing up were about twice as likely to get multiple sclerosis later, compared to people who never got infectious mono," Thacker told Reuters Health.

"The potential implication of our observation is that some cases of multiple sclerosis could probably be averted through the prevention of infectious mono," he said. "One way to accomplish this might be to develop a safe and effective vaccine against Epstein-Barr virus, the virus that causes infectious mono."