WASHINGTON (Reuters) - President Barack Obama said on Wednesday that he was bringing back nearly all U.S. troops fighting the Ebola epidemic in West Africa and marking a new phase in the battle to help countries "get to zero" cases of the deadly disease.

Obama said the outbreak was a "wake-up call" for the world, and that wealthy countries needed to invest to ensure that poor nations have basic health systems to detect and fight diseases.

"This is not charity," he said in a speech at the White House. "The investments we make overseas are in our self-interest."

The year-long Ebola outbreak has now killed at least 9,177 people among the 22,894 cases recorded, mainly in the three worst-affected West African nations of Liberia, Sierra Leone and Guinea.

Obama said the rate of new Ebola cases has dropped dramatically, but that Guinea has the "longest way to go" in stemming the disease.

"Today we move into the next phase of the fight, winding down our military response while expanding our civilian response," he said.

The World Health Organization said on Wednesday that there were 144 new confirmed cases of the disease in West Africa in the week of Feb. 8, the second weekly increase in a row, highlighting lingering challenges to end the outbreak.

At least 10 people are known to have been treated for Ebola in the United States, four of them diagnosed with the disease on U.S. soil.

Only two people are known to have contracted the virus in the United States - both of them nurses who treated an Ebola patient from Liberia who became sick and died in Dallas in October.

After that incident, Obama was excoriated for the slow U.S. government response to Ebola. On Wednesday, he said his approach proved skeptics wrong, and he criticized some unnamed people for "sensationalism" that stoked public fears about the disease.

"There are those who like to fan fears, but over the long haul, America does not succumb to fear," Obama said.