President Obama opened the final day of the unprecedented US-Africa summit in Washington, saying African nations are growing stronger despite the many challenges they face.

Colonial poverty, then civil war, and now, a deadly plague.

Among the world's poorest states at the bottom of global development indexes, Sierra Leone, Liberia and Guinea had shown signs of leaving behind brutal wars and leaping into Africa's economic boom - before a lethal Ebola epidemic struck.

As the world's biggest outbreak ravages the populations of these small states from West Africa's Mano River Region, their resource-dependent economies are reeling from the impact.

With the death toll more than 900, Ebola is hitting tourism, reducing travel and trade, and slowing farming and mining, delivering body blows to what had been buoyant GDP growth driven by increasing foreign investment, officials said.

"A common feature of these three countries is they're all fragile states," Makhtar Diop, the World Bank's vice president for Africa, said on a call with reporters.

"It means that they're countries that need more support from the international community in normal times ... And this external shock that they're currently facing, this crisis, is taking them even further back," Diop said.

Liberia's Finance Minister Amara Konneh said the outbreak had already cost his country's economy $12 million between April and June - two percent of the budget - and the disease was still spreading. Liberia would have to revise down its projected GDP growth of 5.9 percent, he said.

"We are scrambling for a response for this crisis ... If it is not contained it will have serious consequences for our economy," Konneh told Reuters.

In the ramshackle ocean-front capital Monrovia, still scarred by a 1989-2003 civil war, relatives of Ebola victims were dragging bodies into the dirt streets rather than face quarantine enforced by troops.

Sierra Leone's foreign minister, Samura Kamara, said his country could ill afford the costs of fighting the epidemic.

"You have to divert resources. You have to divert energy. So you are slowing down the other aspects of real economic development just to fight a disease that erupted out of nowhere," he told Reuters on a visit to Washington.

An initial World Bank-IMF impact assessment for Guinea, where the outbreak started in a remote forest region and has killed over 350 people, projects the bauxite exporter's GDP growth falling from 4.5 percent to 3.5 percent.

The World Bank and African Development Bank have committed $260 million to help the three worst-affected countries.

With two Ebola deaths also reported so far in Nigeria, fears are growing about how the deadly virus, which can kill up to 90 percent of those it infects, could impact Africa's top oil producer and most populous nation, and the surrounding region.


FLEEING FARMERS, FALLING REVENUES

The World Bank said agriculture had been hit in Guinea, Sierra Leone and Liberia as rural workers fled farming areas in the affected zones, where some Ebola patients have been shunning medical treatment and hiding away in their villages.

Liberia's Konneh said a slowdown in farming and transport and reduced activity at popular markets could push up prices of essential food items and other goods.

"We're watching inflation. So far it's not been bad but we're worried about the Lofa food belt where people are quarantined and major markets closed. We expect hoarding by people in urban areas that could drive food prices up," he said.

In Monrovia, residents said the Ebola emergency, and the fear and suspicion it has generated, was disrupting daily life, affecting everything from street hawking to taxi fares.