The location of the Ebola outbreak has flipped the script on the disease's containment, one of the nation's top Ebola experts told NBC News on Saturday. Because the illness has spread to four countries and taken root in urban areas, more cases are likely to occur, said Dr. Jeffrey Koplan, vice president for global health at Emory University and former director of the Centers for Disease Control and Prevention. While previous Ebola outbreaks were controlled within weeks, Koplan said containment this time "is clearly going to take months" and will take "more effort, more personnel and more equipment" as the disease continues to move to new places.

Previous outbreaks have occurred mostly in rural areas, including ones in Uganda and along the Sudanese border, and all were able to be controlled. The less densely populated locations meant that the outbreak was "much more self-limited," Koplan said, which allowed for a quicker and more effective response. While Koplan warned that the current Ebola crisis is "not going to turn around overnight," he said public health officials can practice and apply what they know about the disease to control it successfully.

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— Jacob Passy and Gabe Gutierrez