Francisco Ferreira told a lecture in Johannesburg that successful containment of Ebola in some West African countries made its gloomiest forecasts less likely, although economic damage could still escalate if there was any complacency.

"The risk of the highest case of economic impact of Ebola has been reduced because of the success of containment in some countries. It has not gone to zero because a great level of preparedness and focus is still needed," Ferreira said.

"I would say the outlook has moved closer to the lower case of $3-$4 billion, than the upper case ($32 billion)," he added.

Ferreira said, however, that the Ebola crisis had already ravaged tourism in Africa because the "fear factor" kept visitors away from countries even where there had been no cases of the virus, like Kenya and South Africa.

In a report in October on the possible economic impact of the Ebola epidemic, the World Bank had said that if the virus spread significantly outside the epicenter states of Guinea, Sierra Leone and Liberia, this could potentially cost Africa tens of billions of dollars in disrupted cross-border trade, supply chains and tourism.

The bank said a scaled-up global response was needed to prevent this worst case scenario. Since then, the United Nations has led international efforts to send more medical personnel to the Ebola zone and increase funding to fight the worst recorded outbreak of the deadly hemorrhagic virus.

The latest WHO Ebola tally on Nov. 14 reported 5,177 deaths out of 14,133 cases, mostly in the three worst-hit countries.

Ferreira also highlighted a more than 30 percent drop in global oil prices since June as a major concern for the fiscal stability in African oil producers, particularly the continent's largest crude exporter, Nigeria.