Skinny and gap-toothed, her nose smudged with black dust, grandmother Kanotu Mumo sorts charcoal into small pots for sale on the stoop of her slum hut.

Mumo is an ?AIDS granny? in Kibera, one of Africa?s biggest slums. Like grandmothers all over Africa, they have been left to fend for orphans after their own children and husbands died.

Her hut, stacked with sacks of charcoal, measures 10 by 8 feet (3 by 2.5 metres) and is too dark to see more than a few inches (cm) even in the middle of the day.

Somehow she shelters four grandchildren, two great grandchildren and the child of a dead relative, who sleep on mattresses and two beds. There is no toilet or running water.

According to UN figures, at least 12 million children in Africa have lost one or both parents because of AIDS. This is 80 % of all AIDS orphans in the developing world. The number of orphans in Africa has increased by 50 % since 1990 while falling in other regions. The United Nations says there will be 53 million by 2010, some 30 percent of them bereaved by AIDS.

The burden of this disaster is borne by extended families, most often grandmothers, who might have otherwise dreamed of returning to their home villages for retirement at the end of a tough life.

Kanotu Mumo moved to Kibera, home to 800,000 people, when her husband died about 25 years ago in eastern Kenya. ?I can?t remember. It has been so long. When my husband died the relatives threw me out and sold the land.?

Unlike many of the grandmothers, doleful and worn down by their fate, Mumo smiles and jokes. She says she cannot remember her age. As she talks, two teenage granddaughters come and go.

Her story is typical of the everyday tragedies of Kibera. Two daughters and a son died of AIDS. Another son was stoned to death by a mob after he was caught stealing. ?I am embarrassed to talk about it but it was due to the unemployment.?

She lives close to the railway line that runs through the sprawling slum, acting both as a pedestrian thoroughfare and place for traders to lay out shoes and clothes. She sells her charcoal ? the slum?s primary fuel ? for a few shillings profit, after buying from a nearby wholesaler who carries it to her hut.

Like other grandmothers interviewed by Reuters, Kanotu Mumo comes to the Stara school in Kibera to clean twice a week. Their grandchildren attend the school and are fed from huge vats of steaming maize porridge and beans.

The project, supplied and funded by Dutch charity Childs Life International, the UN World Food Programme and Kenyan aid agency Feed the Children, was started seven years ago by a group of Kibera mothers, after friends died and left them to look after their children.

The school on the edge of Kibera houses more than 500 lively children, 70 % of them orphans, dressed in green uniforms. More than 30 of the children are HIV positive and receive anti-retrovirals from a nearby clinic in the slum, supplied against vouchers from the school.

The small size of the premises means classes are noisy and overcrowded, with up to 80 children of mixed ages. The school, headed by dynamic Kibera resident Josephine Mumo, has proven skilful in raising support.

Singer Harry Belafonte, Barbara Bush, mother of President George W. Bush, and actress Drew Barrymore have been backers. Without their grandmothers and projects such as Stara, many more orphans in Kibera and elsewhere would end up as glue-sniffing street children or child prostitutes.

Josephine Mumo says that when the mothers started the school, they brought in children who had been raped as they went door-to-door begging for food.