On the other hand, he said, he was alarmed to hear that on a recent day in Conakry, Guinea’s capital, there were not enough beds for all the patients who needed them. Leaving infected people in the community can lead to exponential spread of the disease, Dr. Frieden said, adding, “That’s what Conakry is at risk of.”

He said he had met with Guinea’s president, Alpha Condé, who told him that the country was working hard to open more treatment units in Conakry.

Dr. Frieden said he was also dismayed to hear about a nurse at Donka Hospital in Conakry, Guinea’s largest hospital, who contracted Ebola after starting an intravenous line on a patient who turned out to be infected. Even though it was six months into the epidemic, the nurse had failed to put on gloves.

Sierra Leone has also been struggling, Dr. Frieden said, noting that many health workers at Connaught Hospital in the capital, Freetown, have died of Ebola and that the hospital is still “largely closed.” At least 10 people a day have been dying in the surrounding community, sometimes at the hospital entrance.