NEW YORK (Reuters Health) - Although studies have found a link between infection with the Epstein-Barr virus and a heightened risk of multiple sclerosis, new findings cast doubt on the theory that the virus helps cause the disease.
In an analysis of spinal fluid and autopsied brain tissue from people with MS, researchers found little evidence of Epstein-Barr genetic material in the samples.
That absence, the researchers say, indicates that the virus is not directly involved in the MS disease process, as a number of other investigators propose.
Multiple sclerosis, or MS, is believed to arise from an abnormal immune system attack on the body's own myelin, a protective sheath surrounding nerve fibers in the brain and spine. This leads to symptoms such as muscle weakness, numbness, vision problems and difficulty with coordination and balance.
Researchers have long suspected that a combination of genetics and an environmental trigger -- such as a virus -- may be to blame for inducing this abnormal immune assault. Studies have particularly focused on Epstein-Barr, an extremely common herpesvirus that causes mononucleosis in some people.
It's believed that nearly everyone -- up to 95 percent of people worldwide -- become infected with Epstein-Barr at some point. After infection, the virus can then take up residence in some of the body's B lymphocytes, a type of immune-system cell, where it dwells in a dormant state.
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