President Barack Obama announced Wednesday that all but 100 American troops sent to West Africa to help manage the Ebola outbreak will be withdrawn by April 30.

The troops were dispatched to help contain the deadly virus, but the President said that the mission in the ravaged countries has shifted. 

"While our troops are coming home, America's work is not done," he insisted. "Our mission is not complete. Today we move into the next phase."

Thousands have died across Guinea, Liberia, and Sierra Leone since the outbreak began last spring. There have been nearly 23,000 confirmed or suspected cases of Ebola infection stemming from the current outbreak as of February 9.

Obama said that the focus has changed from containment to eradication, and said that civilian aid workers will be increased in the area. 

Civilian government employees, volunteers, and the remaining troops will help in that effort. 

"Our focus now is getting to zero," Obama said, calling the military's effort a "hope multiplier." 

"Every case is an ember that if not contained can light a new fire," he added. "Plenty of American heroes remain on the ground, with even more on the way."

The spread of Ebola has slowed, although health officials were concerned about a rise in Ebola deaths last week. For the week ending February 8, 144 deaths were reported, compared to 124 deaths the week before.

"Despite improvements in case-finding and management, burial practices and community engagement, the decline in case incidence has stalled," the World Health Organization wrote. 

Ebola cases in Liberia have generally decreased, while transmissions in Guinea and Sierra Leone continue to trouble health officials.