“Everything that everyone did during those first two heartbreaking weeks will have been for nothing if these patients don’t get continuing care,” said Dr. Elizabeth Bellino, a pediatrician based at Tulane University who worked in Haiti right after the earthquake.

In Uganda now on a project, Dr. Bellino, 34, said she closed her eyes and saw the beaming face of a 12-year-old Haitian boy named Mystil Jean Wesmer who ended up comforting her when she dissolved into tears. As she recounts it, Mystil smiled gently and, sensing that she was overwhelmed by the need around her at a field hospital run by Americans, said: “ ‘Go take care of the sicker kids. I’ll be O.K.’ ”

He himself was waiting to have his leg amputated.

“All he wanted to know was how he was going to walk to school and church,” Dr. Bellino said. “I said, ‘Well, we’ll figure that out.’ But now I’m so worried about him, about all the kids.”

Dr. Pierre, a Haitian-American who is the director of pediatric intensive care at the Brooklyn Hospital Center, said he thought constantly about the patients he left behind, too. Even as he plans his next trip — he and Dr. Stephen Carryl, the chairman of surgery at his hospital, will be returning with a prosthetics maker — a few memories plague him.

Back in Brooklyn, he still hears the loud, shrill cry of a mother at the moment her small son died of a raging infection on the lawn of a hospital in the Carrefour neighborhood. The mother and father, one child already lost to the earthquake, had implored Dr. Pierre to help their 4-year-old, who had been eviscerated by a concrete block and hurriedly stitched back together by a local doctor.