Epstein=Barr virus is a very common type of herpes virus. Nine out of ten adults will be infected with EBV in their lifetime. Usually it causes no symptoms. In some people, EBV causes glandular fever, also known as mononucleosis.

After a viral infection, immune cells remember what the virus looks like to attack it again. The immune cella could be mistaking myelin for EBV. Research shows parts of myelin look similar to parts of the EBV virus.