So, if this outbreak is Zaire-strain-based, with only moderate genetic divergence over time, what accounts for the drop in death rates? Better supportive measures or lower mortality of the strain (could be accompanied by a greater level of infectiousness).
Potentially lower mortality.
I’m not sure how supportive measures have changed though. Maybe early testing has gotten better to start the supportive measures earlier?
This is another good article:
http://www.bbc.com/news/science-environment-20341423