Its kill rate: In this particular outbreak, a running tabulation suggests that 54 percent of the infected die, though adjusted numbers suggest that the rate is much higher.
Its exponential growth: At this point, the number of people infected is doubling approximately every three weeks, leading some epidemiologists to project between 77,000 and 277,000 cases by the end of 2014.
The gruesomeness with which it kills: by hijacking cells and migrating throughout the body to affect all organs, causing victims to bleed profusely.
The ease with which it is transmitted: through contact with bodily fluids, including sweat, tears, saliva, blood, urine, semen, etc., including objects that have come in contact with bodily fluids (such as bed sheets, clothing, and needles) and corpses.
The threat of mutation: Prominent figures have expressed serious concerns that this disease will go airborne, and there are many other mechanisms through which mutation might make it much more transmissible.