The U.S. military mission to help contain the Ebola virus has begun winding down as hundreds of troops return home from West Africa earlier than expected.

The total number of U.S. troops in West Africa, 2,542, is down from a peak of about 2,900 in December, Army Lt. Col. Valerie Henderson said Tuesday.

Another 86 soldiers are scheduled to return to Fort Hood, Texas, on Wednesday and begin a 21-day quarantine at a facility there, Henderson said.

The number of new Ebola cases reported in Liberia has dropped dramatically since U.S. troops arrived and began building treatment facilities and providing logistical support for the civilian-run health care system.

Health officials reported about 31 new Ebola infections in Liberia during the final week of December, compared to a peak of more 300 new cases each week in August and September, according to recent data from the World Health Organization.

The U.S. military scaled back its mission in several ways since initial planning began last summer. The original plan projected that 4,000 troops would be needed to build 17 treatment facilities with 100 beds each.

Now, it appears that the force topped out at about 2,900 in December and the construction mission was reduced to 10 treatment facilities, some with only about 50 beds, officials said.

All returning troops must remain in quarantine for 21 days in one of several designated facilities in Europe or the U.S.

As of Tuesday Jan. 6, a total of 425 troops have redeployed and competed the quarantine, which military officials call "controlled monitoring."

Some 199 remain in quarantine, about half at a facility at Joint Base Langley-Eustis, Virginia, the other half at Joint Base Lewis-McChord, Washington, Henderson said.

The military's mandated quarantine policy has been controversial because it is not required for civilians and many health officials say it is unnecessary for people who show no symptoms.

The Pentagon is reviewing the policy. Chairman of the Joint Chiefs Army Gen. Martin Dempsey will submit a recommendation to the defense secretary by Jan. 30 31 about whether the quarantine is necessary and effective.

The military mission is driven in part by requests for support from the civilian-run U.S. Agency for International Development, which is leading the humanitarian mission.

Ebola infections remain on the rise in Guinea and have only begun to decline in Sierra Leone, health officials say.

USAID could request additional military support in other African nations fighting to contain the Ebola virus, military officials say. But for now there has been no such request.

In total, health officials say here have been 20,206 reported cases of Ebola virus infection, with 7,905 reported deaths. No U.S. service members have contracted the virus.