The key is reactivation of the virus vs carrying the virus.

Think of the analogy of people who get cold sores. The virus lays dormant in the system and sometimes gets stirred up producing a cold sore. So the percentage of people who carry herpes virus in this example is much higher than the percentage of people who have it active at any given time.

With ebv, 95% of people have it and somewhere around 3 to 5% of people have it reactivate. When it reactivates, it can activate autoimmune processes such as MS as well as being directly inflammatory.

In the study on MS noted, most who had MS had EBV. The likelihood is that most of those actually had reactivated EBV.