“This epidemic has unearthed a lot of the weaknesses,” he said.

Soon Ebola dominated Dr. Kim’s schedule. On Aug. 4, during the African leaders’ summit meeting in Washington, the bank announced $200 million for the outbreak, most of it grants. When he told President Johnson Sirleaf that the bank would be sending urgently needed money to pay the salaries of community health workers, she replied, “This is the best news I’ve had all week,” according to an account of the conversation by someone on the call.

“He’s made the bank move fast in ways that I’ve never seen it move fast before,” Dr. Frieden said.

Lessons in Leadership

Dr. Kim grew up in Muscatine, Iowa, the son of a dentist. He was valedictorian of his high school class and played quarterback for the football team and point guard on the basketball team. He developed an interest in geopolitics through meetings at the Stanley Foundation, a think tank founded by the furniture and engineering magnate Claude Maxwell Stanley. But it was his mother’s neo-Confucian view — knowledge is useless unless it leads to self-reflection and moral behavior — that led him to activism, he said.

Dr. Kim and Dr. Farmer had epic battles with the broader public health world by insisting that the poor should have the same treatment as the rich. Many criticized that approach as unrealistic, but their work in Haiti and Peru offered some evidence that complex health solutions could work even in poor places. In Haiti, for example, locals were paid small sums to visit people with AIDS and make sure they took their medicine, and mortality plummeted.

Now, he believes, that approach can be applied to Ebola, though critics say the situation is so desperate that it is less a matter of systems than of speed in scaling up treatment. (Dr. Kim has enlisted Dr. Farmer, who is not being paid by the bank, to do just that.)

“He’s an activist and he wants to get things done,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. “He’s quite an analytical person, but he doesn’t analyze to the point of paralysis.”

But he has alienated many of the bank’s career professionals at a time when he needs them to deliver on his ambitious agenda on Ebola and, more broadly, on combating extreme poverty.