I am convinced mine was caused by a virus. I remember I was about 24, waiting for my boyfriend to have his haircut and I was feeling cold. Suddenly I got the shakes, I was so frozen it was uncontrollable. Ok it was winter but I was indoors. I was out cold for a week or two, on antibiotics.
It was not long after that that I had my first ms symptoms.
I was never sick as a child, had few illnesses as a teen, so I am thinking my immune system was not too good. Also I was not breast fed. If all this adds to immune system weakness then I guess a virus has everychance of causing severe damage.
best

J.