A shortage of money and personnel threatens to derail progress against West Africa's Ebola epidemic, as health officials race to stop the outbreak before the onset of the region's rainy season in April, the World Health Organization said.

The WHO only has $90 million of the $350 million it needs for its Ebola effort for the next six months, Bruce Aylward, the agency's assistant director-general in charge of response to the disease, said at a briefing in Geneva today. Aylward's comments followed those of David Nabarro, the United Nations' special envoy for Ebola, who said on Jan. 21 that the UN is seeking another $1 billion in donations for organizations including the WHO to fight the outbreak.

Efforts to identify and isolate cases and their contacts, and ensure safer burials, have helped drive the number of new infections to the lowest levels since August in Guinea and Sierra Leone, and the lowest since June in Liberia, Aylward said. The costs of ending the epidemic increase as cases go down, as disease detectives fan out across the region to track down every last infection, he said.

"If we cannot close that funding gap, we will snatch defeat from the jaws of victory," Aylward said. "The biggest risk to getting this finished, is not complacency, it's not fatigue. The issue is financial resources and people."

At its current spending rate, the WHO will run out of money for its Ebola response in mid-February, Aylward said.

"That's four or five months before the virus is going to stop in a best-case scenario," he said.