BRUSSELS (AP) — The U.S. ambassador to the United Nations, returning from a visit to West Africa, which has been struggling with the world’s worst Ebola outbreak, says the world must do more to confront “the greatest public health crisis ever.”

Ambassador Samantha Power said Thursday that efforts by the United States and other countries to combat the spread of the deadly virus have begun to bear fruit but that “we each have to dig deeper.”

Without naming them, she said some nations had yet to shoulder their fair burden in the battle against Ebola.

Power spoke to an audience in Brussels after visiting the three countries hardest-hit by Ebola — Liberia, Sierra Leone and Guinea –earlier this week.

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