KENEMA, Sierra Leone — The best defense against despair was to keep working. Many times, that choice was far from obvious: Josephine Finda Sellu lost 15 of her nurses to Ebola in rapid succession and thought about quitting herself.

She did not. Ms. Sellu, the deputy nurse matron, is a rare survivor who never stopped toiling at the government hospital here, Sierra Leone’s biggest death trap for the virus during the dark months of June and July. Hers is a select club, consisting of perhaps three women on the original Ebola nursing staff who did not become infected, who watched their colleagues die, and who are still carrying on.

“There is a need for me to be around,” said Ms. Sellu, 42, who oversees the Ebola nurses. “I am a senior. All the junior nurses look up to me.” If she left, she said, “the whole thing would collapse.”

The other nurses call her Mummy, and she resembles a field marshal in light brown medical scrubs, charging forward, exhorting nurses to return to duty, inspecting food for patients, doing a dance for once-infected co-workers who live — “nurse survivors,” she called them enthusiastically — and barking orders from the head-to-toe suit that protects her from her patients.