Ebola is a severe, often fatal disease that first emerged or was discovered in 1976 and has killed 90 percent of its victims in some past outbreaks. Since March of this year there have been more than 1,700 cases of Ebola, including more than 900 fatalities in Guinea, Liberia, Sierra Leone, and Nigeria. This time, the average fatality rate in this outbreak is estimated at 55 percent, ranging from 74 percent in Guinea to 42 percent in Sierra Leone. The disparity in mortality rates is partially linked to the capacity of governments to treat and contain the disease and per capita health spending by affected governments. There is also concern that given modern air travel and the latency time of the disease, the virus will jump borders and threaten lives elsewhere in Africa and even here in the United States.