Yes there is probably a particular virus that’s involved. It is EBV, unfortunately a very common virus that can get reactivated by COVID-19. The picture only got clear this year and there are no great therapies or vaccines yet. In this study from earlier this year, the chance of active military developing MS was 32-times (3,200%) higher for people who had EBV vs those that had other common viruses: https://www.science.org/doi/10.1126/science.abj8222