Kabul (CNN) -- Five-year-old Marjan sniffles from the cold as she struggles under her load. Hoisted on her back is a bag almost as big as she is.
Instead of going to school, Marjan scavenges for hours with her 10-year-old aunt collecting trash. It is a heavy burden for such a small child but a necessary one. The trash she collects is what her family uses as fuel for cooking and, more importantly, to fend off Kabul's bitter winter.
It is a matter of life and death for someone so young. Last winter, Marjan's baby brother died from the cold.
"It was dark and cold, and the baby died," she says softly, wiping her running nose. "I saw him dead and I was very sad, and I cried."
"I don't blame myself," Marjan's mother, Zarkharida, says. "We don't have firewood. I set fire to the garbage but it went out and my baby died."
Zarkharida's husband was killed in a family feud over land. She was forced to move in with relatives, already struggling to make ends meet. She built a one-room mud hut on a small piece of land.
"I wasn't able to properly cover the roof, this is why when the cold weather came my son died," she says.
Plastic tarp covers the roof, windows and doorway. She stitched a blanket from scraps of clothes given to her as charity. It is all she has to keep her family warm.
But Zarkharida fears this winter will claim another one of her children.
"Of course I am worried about my children's health," she says. "I am afraid they will get sick."
UNICEF, the UN children's agency, says that Afghanistan is the worst place in the world to be a child. One in five children do not live past the age of five. Afghanistan is second only to Sierra Leone when it comes to child mortality. Most of those deaths are caused by curable childhood diseases and malnutrition, compounded by the security situation, which means that parents are unable to access proper health care.
"It is very hard to put a hard and fast figure to the number of children dying from hypothermia alone on Kabul's streets as there would undoubtedly be other reasons that would make them sick or vulnerable in the first place," UNICEF regional communications chief Sarah Crowe wrote in an e-mail. "Extreme poverty, having lost a parent, being trafficked or displaced, or many other reasons may have forced them on to the streets where they would be deprived of their most basic needs (decent food, health, immunization, protection) and exposed to the extreme cold of Afghan winters."
Marjan is constantly blowing warm air on her hands, which are grimy and cracked from the cold. She kicks off her plastic, torn shoes and tries to warm her feet on the trash fire blazing under the kettle. But it is never enough.
A meal is scraps of bread and weak tea.
Even though she has never set foot in a classroom, Marjan dreams of being a teacher. She also loves to play with dolls. But in one of the world's poorest countries, she is, instead, responsible for her family's survival.