There is a new analysis out regarding the quarantine period for Ebola here.

Quote:
While the 21 day quarantine value currently used may have arose from reasonable interpretation of early outbreak data, this work suggests a reconsideration is in order and that 21 days may not be sufficiently protective to public health.


It's rather technical, but the bottom line is:

Quote:
A 21 day period for quarantine may result in the release of individuals with a 0.2 – 12% risk of release prior to full opportunity for the incubation to proceed.