[1] doesn't cover how many others an Ebola patient infects, which is the reproductive ratio per [2] and basic reproduction number or R <subscript> 0: https://en.wikipedia.org/wiki/Basic_reproduction_number

It's above 1, by my and many other's estimates around 3 in this outbreak, which, while technically "isn't particularly infectious", is still very bad and quite enough for exponential growth, in this case with an observed doubling time of 3-4 weeks. The CDC's recent worst case estimate is 1.4 million infections by January.