http://news.nationalgeographic.com/news/2014/10/141012-ebola-dallas-healthcare-spread/

As of Oct 10th via the WHO report on the outbreak: At least 416 health care workers have been infected with Ebola in West Africa this year and 233 have died, greatly limiting the care options there, and the willingness of others to provide that care. In total, more than 8,300 people have been infected by Ebola this year and about 4,000 have died.

So, out of 8300 infections, 416 have been health care workers even though the level of contact between health care and infected patients is very limited there. So, with even limited contact there is a 5% incident rate for health care workers. I understand that they also may have limited resources to help prevent the spread as well. Of those 416, more than half have died. These are people who take care of sick people for a living, have seen what this disease can do, and would most likely seek immediate treatment. The odds are relatively low of contracting it based on the numbers, but once you get it, you're looking at less than a 50/50 chance of survival, which is what makes it so devastating.