President Barack Obama urged other countries, foundations and businesses to step up their contributions to the global response to Ebola, calling the disease a “threat to the world” while emphasizing that the U.S. would keep leading the effort.

“There’s still a significant gap between where we are and where we need to be,” Obama said in remarks prepared for a speech today at the United Nations General Assembly in New York. “We know from experience that the response to an outbreak of this magnitude needs to be both fast and sustained, like a marathon, but run at the pace of a sprint. That’s only possible if every nation and every organization does its part. And everyone has to do more.”

Hitting Liberia hardest and four other West African countries, the Ebola virus has killed at least 2,800 people and infected nearly 6,000, according to a Sept. 22 World Health Organization report. The World Bank has said the economic costs of the outbreak will be “catastrophic” if the virus continues to spread.

The disease may cost Guinea, Liberia and Sierra Leone, the three nations where most infections have taken place, as much as $809 million, the World Bank said on Sept. 17.

The Centers for Disease Control and Prevention, which Obama visited last week to talk about Ebola, assumes in a worst-case model that cases are “significantly under-reported” by a factor of 2.5. With that correction, the CDC predicts 21,000 total cases in Liberia and Sierra Leone alone by Sept. 30.

U.S. Troops

Obama pledged Sept. 16 to send 3,000 troops to the region and help build many as 20 100-bed treatment centers. Obama said the U.S. also would train about 500 health-care providers in the region.

The president used one of two addresses this week to the UN to call for more spending, medical equipment and personnel to help the impoverished African countries of Guinea, Liberia and Sierra Leone.

Obama tomorrow in Washington will host a summit on global health security with representatives from 44 countries. The event was announced in February, two months after the first cases in the largest Ebola outbreak in history appeared.