Bell said there are several reasons the outbreak took such a deadly turn.
First, West Africa was not used to dealing with Ebola since this is the first outbreak in the area. The fact that three separate countries are involved also makes the "meticulous public health contact tracing" needed to control Ebola more difficult, as does the fact that there are cases in urban areas.
Lastly, she said, "these countries do not have strong health-care systems and sort of getting around all the various aspects of meticulous field work that needs to be done is hard for them."
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However, Bell noted that it is important to remember that Ebola is not easily spread.
"Ebola is not transmitted through the air, through food or through water. It really requires close personal contact."
She said that so far, there have been about 30 inquiries about the disease from various providers around the country, and the few specimens that have been tested have been negative
Two infected Americans have been flown from West Africa to an Atlanta hospital for treatment, and relief groups have said their conditions have improved after being given an experimental drug.
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However, Bell said she does not know if the treatment has helped, hurt or has had no effect.
Tom Frieden, the director of the CDC, told Congress Thursday he is confident the outbreak will be stopped. He also said the agency is working with National Institutes of Health, Food and Drug Administration, Department of Defense and others to see whether there can be new, effective treatments for the virus.
—By CNBC's Michelle Fox