A simple blood test can evaluate if you have had EBV or have never been exposed to it. You will have anti-bodies to the virus. It can tell if it is currently active or just lying dormant in your body. I believe, IMO only, it can be reactivated, just like PR, and B19, perhaps that's part of a MS relapse.

Many PWMS find when they get sick their symptoms worsen, or a relapse can start in those with the relapsing tag.

95 percent of the population has anti-bodies to EBV in their blood, maybe like the study above, we know not all will get MS but 100 percent of MS people in the trial did have prior EBV exposure.

So let's say, having a predisposition to get MS, birth to 15 years of age (in changing climates areas) we just have a weakness to pick up the EBV more than the people without MS. Not the other way around. Therefore, not everyone with EBV anti-bodies will get MS. Chicken and the egg again.
JMO and thoughts on this topic.