The Pentagon doesn’t plan to deploy the full 4,000 U.S. troops to Ebola-stricken Liberia — scaling back the number even as the virus makes rapid gains elsewhere in West Africa. Army Maj. Gen. Gary Volesky, who’s leading up the effort overseas, said the current 2,200 troops will grow to nearly 3,000 by mid-December. But the military doesn’t expect more soldiers on the ground will be necessary.

The troops have been tasked with building 17 100-bed treatment centers for Ebola, and have already built a 25-bed facility for medical personnel who contract the disease. The World Health Organization said 19 of 53 treatment centers planned in Guinea, Liberia and Sierra Leone are operating.

U.S. Health and Human Services Secretary Sylvia Burwell told lawmakers on Wednesday that the U.S. Ebola response in West Africa is beginning to have an effect on the worst-ever outbreak of the deadly virus.

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“We are optimistic that our strategy is starting to have an impact, with declines in the number of new cases in parts of Liberia,” Burwell said in written testimony to the Senate Appropriations Committee. "However, progress is fragile and fluid, the number of new cases in Sierra Leone is still growing, hot spots continue in rural, remote parts of Guinea and Liberia, and more work needs to be done, especially to scale up,” she added.

The number of Ebola deaths in West Africa has risen to 5,147 out of 14,068 cases at the end of Nov. 9, WHO announced Wednesday. In addition, the country of Mali — not considered the epicenter of the outbreak — has seen a total of four confirmed and probable Ebola cases and four deaths.

Speaking on the phone call to reporters at the Pentagon, the U.S. ambassador to Liberia, Deborah Malac, said the Ebola crisis in Liberia is not over. “We are not out of the woods by any stretch of the imagination,” she said.

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Maj. Gen. Volesky, cmdr. of Operation United Assistance, says U.S. will send up to 3,000 troops to Liberia, down from orig estimate of 4,000 — Felicia Schwartz (@felschwartz) November 12, 2014

— Jim Miklaszewski and Tony Capra

Reuters contributed to this report.