March 25, 2003 -- There is new evidence linking the virus that causes mononucleosis with an increased risk for multiple sclerosis, but experts say it is unlikely that Epstein-Barr virus infection alone triggers the degenerative nerve disease.
"Epstein-Barr virus [EBV] is intriguing, but it is not the whole story," National Multiple Sclerosis Society spokeswoman Patricia O'Looney, MD, tells WebMD. "EBV is very common, with 95% of people becoming infected by age 40. Obviously if it were a simple association, a lot more people might have MS."
Researchers have searched for decades for a viral or bacterial cause for multiple sclerosis, which affects some 350,000 Americans and causes symptoms ranging from slight numbness to complete paralysis. Fifteen months ago, researchers from Harvard University School of Public Health used blood samples taken from more than 60,000 women to show a link between the common herpes virus, EBV, and multiple sclerosis. Those who later developed MS had significantly higher levels of EBV antibodies in their blood than a comparison group of women who did not get the disease.
The researchers used a similar design in their latest study, but this time they analyzed blood samples collected from more than 3 million active duty and reservist military personnel. Samples were collected between 1988 and 2000, and 83 cases of multiple sclerosis were later identified through disability records. The findings are reported in the March 26 issue of TheJournal of the American Medical Association.
The average time between collection of blood samples and the diagnosis of MS was four years -- roughly two years longer than in the previous study. And just as in that study, antibody levels to EBV were consistently higher among the MS patients than among study participants without the disease.
"To me, these data strongly point to some sort of causal relationship between EBV and MS," lead author Alberto Ascherio, MD, tells WebMD. "But this is a very controversial topic, and people are very skeptical because there have been claims about different infectious agents in the past."
Ascherio says more evidence of a link can be found in research suggesting that people who avoid EBV infection don't get MS. And he says there is nothing contradictory in the fact that EBV is so common and MS is relatively rare.
"It seems analogous to smoking and lung cancer," he says. "Only a small percentage of smokers get lung cancer, yet we know there is a causal association between the two."
But O'Looney, who is director of biomedical research for the National Multiple Sclerosis Society, says much more study is needed to confirm an association between EBV and MS.
"You certainly can't say from this research, or earlier research, that EBV causes MS," she says. "We know that there is a genetic component involved, and there may be multiple viral or bacterial triggers that could be different for different people. It is just too soon to say."