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In a longitudinal study over two decades in the making, researchers at the Harvard T.H. Chan School of Public Health found that Multiple Sclerosis, a chronic inflammatory disease that affects the central nervous system, is “likely caused” by infection with Epstein-Barr virus.

The research study, a team effort led by Harvard Chan School Professor of Epidemiology and Nutrition Dr. Alberto Ascherio, was published in the Jan. 13 issue of Science. It provides evidence in support of a longstanding theory that EBV is linked to the pathogenesis of Multiple Sclerosis.

Signs of infection with Epstein-Barr virus, which affects over 90 percent of the adult population worldwide, have been found at high rates in MS patients by multiple previous studies, which suggests a connection between EBV and MS but is not conclusive evidence of a causal relationship.

“The idea that the EBV, the Epstein-Barr virus, is associated with multiple sclerosis has been around for many years, but the main problem is that EBV is nearly ubiquitous,” Dr. Ascherio said. “There is this curse of the ubiquitous exposure [to EBV] where it’s not that it cannot cause a rare disease, but it’s just difficult to prove.”

Over a 20 year time period, the researchers examined blood serum samples taken every two years from active-duty U.S. military personnel whose initial serum samples were negative for EBV. Ascherio explained that they were looking to establish the sequence of events for when patients first became infected with EBV and when they were diagnosed with MS.

“We found that they cannot get MS basically, unless they were first infected with Epstein-Barr Virus,” Ascherio said. “That clearly established that you first have to be infected [with EBV], then you can have the beginning of the pathological process that leads to MS.”

Ascherio said the study also represents a critical step towards eventually developing a cure for MS and improving upon the treatments currently available.

“The implication is that if we could prevent infection [with EBV], then we could prevent Multiple Sclerosis, so there is ongoing research on an EBV vaccine,” Ascherio said.

“We are collaborating with clinical investigators to explore the possibility of testing antiviral drugs in people with MS to see if those can improve treatment,” he added.

Despite the causal relationship between EBV and MS established by this study, developing MS is still relatively rare for people infected with EBV, according to Ascherio.

Dr. Ascherio also acknowledged the contributions of several key members of the project including Senior Research Scientist Kassandra L. Munger, and postdoctoral research fellows Kjetil Bjornevik and Marianna Cortese.

—Staff writer Paz E. Meyers can be reached at paz.meyers@thecrimson.com