Thirty-five of the Congo patients have died, the W.H.O. said, including seven health care workers. Isolation facilities have been established in the four affected villages, the W.H.O. said, and international experts assisting local health officials have identified 386 people who may have been exposed.

The International Monetary Fund said Thursday that economic growth in Liberia and Sierra Leone, two of the three West African countries hit hardest by the outbreak, could decline by as much as 3.5 percentage points because of disruptions to the mining, agriculture and service industries. Economic growth in Guinea, the third worst-afflicted country, where mining businesses have yet to be affected, could fall by 1.5 percentage points, the I.M.F. said.

In Nigeria, Africa’s most populous country, where health officials have confirmed 19 Ebola cases, a South African woman in transit at Lagos airport on her way home from Morocco had been sent to a testing center as a suspected Ebola patient, according to Reuters. The woman, who was not identified, had visited Sierra Leone and Guinea.