Study: More evidence links a virus to multiple sclerosis

There’s more evidence that one of the world’s most common viruses may set some people on the path to developing multiple sclerosis.

Multiple sclerosis is a potentially disabling disease that occurs when immune system cells mistakenly attack the protective coating on nerve fibers, gradually eroding them.

The Epstein-Barr virus has long been suspected of playing a role in development of MS. It’s a connection that’s hard to prove because just about everybody gets infected with Epstein-Barr, usually as kids or young adults -- but only a tiny fraction develop MS.

Thursday, Harvard researchers reported one of the largest studies yet to back the Epstein-Barr theory.

They tracked blood samples stored from more than 10 million people in the U.S. military and found the risk of MS increased 32-fold following Epstein-Barr infection.

The military regularly administers blood tests to its members and the researchers checked samples stored from 1993 to 2013, hunting antibodies signaling viral infection.

Just 5.3% of recruits showed no sign of Epstein-Barr when they joined the military. The researchers compared 801 MS cases subsequently diagnosed over the 20-year period with 1,566 service members who never got MS.

Only one of the MS patients had no evidence of the Epstein-Barr virus prior to diagnosis. And despite intensive searching, the researchers found no evidence that other viral infections played a role.

The findings “strongly suggest” that Epstein-Barr infection is “a cause and not a consequence of MS,” study author Dr. Alberto Ascherio of the Harvard T.H. Chan School of Public Health and colleagues reported in the journal Science.

It’s clearly not the only factor, considering that about 90% of adults have antibodies showing they’ve had Epstein-Barr -- while nearly 1 million...