At the end of the winter, Solidarités went from camp to camp, asking parents who had lost children to sign declarations giving details of the loss, including apparent causes of death, Ms. Bara said.

While the data from the survey is still being compiled, she said, Ms. Bara expects the number of children under 5 who died to total 120. “I would say 100 of them for sure were due to cold weather — despite our help,” she said. “Nobody saw it coming.” That worked out to a mortality rate of 2.5 per 10,000 children per day, establishing it as a full-fledged humanitarian disaster, she said.

An example was the Parwan-e-Se camp, not far from downtown Kabul, where camp leaders last February reported two deaths of children from the cold, but on Wednesday said the final total had been eight, according to Abdul Samad, the camp representative. Two died in a hospital, but the other six died in the camp, he said. “One of them was my own granddaughter,” he said. One of the smaller camps, Parwan-e-Se is home to 100 families, about 600 to 700 residents, he said.

On Wednesday, Ms. Amos, who is on a three-day visit to Afghanistan, toured that camp, largely mud huts in a former vacant lot, walking between open rivulets of sewage and pools of waste and garbage. “Clearly there’s a lot of work we need to do,” Ms. Amos said, acknowledging that the camps’ problems had been chronic and long-term. “The real issue is finding land and helping them to relocate.”

The Afghan government has tried to encourage people in the camps to return to their homes, saying in most places it is now safe enough to do so, but it says that many of the refugees remain because there are better economic opportunities in the capital. Residents disagree and claim their home areas are still too unsafe, and many have asked the Afghan government for land and assistance to build homes here.