The virus itself has not changed significantly. If anything, it is less fatal than other outbreaks. But the mode of transmission is the same, the course of disease is the same.
The difference here is that a “perfect storm” of unfortunate events have conspired to spread the virus. It had never been seen in that part of Africa before, so it was spreading for months before anyone figured out what it was. And during that time, it got into some fairly populated areas. There were a lot of cases by then, in countries that have inadequate health care systems and poor infrastructures due to the civil wars that went on for decades.
One good thing that may come of this is that drugs and vaccines might finally be tested—efficacy can only be tested by challenge with the disease, and there certainly are enough disease-challenged people right now.
I would like to write a grant proposal soon, to do my own study...
The outbreak had been identified in December, 2013, iirc. by MSF (Doctors Without Borders).
Here's an article link from March 2014, where the outbreak had spread from Guinea to Sierra Leone from March, and the cry for help went out then. Fears Guinea Ebola outbreak has spread to Sierra Leone and another from March where the virus had reached the capital in Guinea: Ebola epidemic reaches Guinea capital, UNICEF says
Considering UNICEF was saying anything about the outbreak, the UN and the WHO should have been fully aware at least seven months and thousands of deaths ago what was going on.
There has been ample time to 'do something', the problem has been known, and yet this has been treated with the 'past outbreaks burned themselves out and this will too' complacency which has cost thousands of lives so far, and will likely cost thousands more.
The virus has also mutated roughly 400 times since the outbreak, and that is what is believed to have caused false negatives in tests for the disease. Variance from Ebola Zaire has been enough that I have seen this referred to as Ebola Guinea. (The links are in the Surveillance Thread, and I just do not have time to dig them out, feel free to browse there if you do not recall this yourself.)
Not all mutations are beneficial for the organism, obviously, but there has been change with the unprecedented number of replications that have occurred in an unprecedented number of vicitms.
(There is a possibility the infected had not progressed far enough for the virus to be detectable, but if that is the case, the tests need revamping.)
This outbreak is also unprecedented in the sense that it is in urban areas, not just outlying villages, and that changes things. It may or may not be the same pathogen (+/-3%), but the playing field is different when it comes to proximity of potential victims, transfer time from patient to fomite to unsuspecting victim, and the raw potential for increased effectiveness of transfer that comes with the sheer number of potential hosts.
A .10% chance of infection isn't so bad when there are only one or two people, but a thousand people pretty much guarantee someone is going to get sick.
This outbreak is already more fatal than the Uganda outbreak, and the numbers are far from complete. Please also compare dead today vs total infected 2-3 weeks ago, because that is a more likely accurate measure of the kill rate.
With the number of infected doubling within the incubation period, the current pending outcomes will skew the death rate downward if you compare today's total cases with today's cumulative dead. To say otherwise is bad science.