The World Health Organization has declared a rare Ebola outbreak a public health emergency of international concern, with its chief warning that the number of suspected cases, currently at 600, and 139 suspected deaths, is expected to climb significantly. This grim forecast comes as the virus circulated undetected for some time before the outbreak was identified.

The World Health Organization has triggered its second-highest international alert level in response to the Ebola epidemic in the DRC.

"There are significant uncertainties to the true number of infected persons and geographic spread," the Geneva-based body warned