How likely is it that ebola will spread in the united states?

Unlikely: We may see an imported case that sneaks through surveillance but that is unlikely. And while infection control practice and quarantine in the US is pretty good, you can bet the CDC and public health authorities will make sure it is picture perfect if such a case is detected. Any spread will be immediately limited. Health Care Reform will likely be blamed for any breach .

Extremely unlikely: Many barriers are in place and the recognition is sufficient that any case would be quickly isolated. It could be spread by bioterrorism but the risk to those trying to produce this in the first place would be considerable and they would likely contact it and die well before they got it to the USA