Marburg is not a good candidate for a pandemic because it is not spread by airborn viruses but by direct contact with infected bodily fluids through a break in the skin or mucus membranes. In other words, the Marburg virus spreads the same way that the AIDS virus does. So maybe a breakout in the gay community, or from to contaminated blood, but not a pandemic.
It's a modified Marburg virus. It doesn't even need to spread for it to be made into a pandemic 2.0