There is a summary Wiki page which covers what the WHO and CDC are saying.
Notwithstanding the dire statistic of the "R" number in Liberia and Sierra Leone, the virus is not currently taking off in countries with a slightly higher capacity to respond (such as Nigeria). Within the gloom the apparent confinement of the virus is a small ray of light. Clearly multiple factors must combine to put the R into the 1.4 - 2.26 range.
"In a 23 September CDC report, a projection calculates a potential underreporting which is corrected by a factor of 2.5. With this correction factor, approximately 21,000 total cases are the estimate for the end of September 2014 in Liberia and Sierra Leone alone. The same report predicted that total cases, including unreported cases, could reach 1.4 million in Liberia and Sierra Leone by 20 January 2015 if no improvement in intervention or community behavior occurred.[216]" [my emphasis]
