Of course, this does not prove that EBV alone causes Multiple Sclerosis. Since most of the adult population is infected with EBV, and only a very small percentage of those infected develop MS, the virus alone cannot be the sole cause of the disease. More likely, a combination of genetic predisposition, Epstein-Barr infection, and some other trigger, such as vitamin D deficiency, sets off the anomalous immune reaction that is called Multiple Sclerosis.
As a leading epidemiologist said, the study does show that "people who are not infected with EBV do not get MS". The study also found that subjects without MS who had the highest levels of EBV antibodies were at the highest risk of developing MS at some later time.
This topic has come up from time to time on many of the Internet MS forums, and some patients always strongly object, stating that they couldn't be infected with Epstein-Barr virus, because they've never had mono. The fact is that most people who carry EBV are completely unaware that they are infected with the virus. EBV infections can be asymptomatic, or may be mistaken for a cold or flu. Using myself as an example, I have tested positive for EBV, but have never had mononucleosis.
My neurologist, Dr. Big Brain, told me several years ago that every MS patient is infected with EBV. He was right. That’s why I call him Dr. Big Brain.