Hawa is an Aids orphan. There are some 1.4 million of them in Kenya, and they have all lost at least one parent to Aids. At the current rate, their numbers could reach a catastrophic level of two million in a year. Like many others, Hawa is also infected with HIV, transmitted to her by her mother during birth. 
Swathed in a large veil, Hamida is an elegant 60-year-old Muslim. Her face is careworn. Three of her five children are no longer alive. Her granddaughter, Hawa, 13, Hawa, is by her side. They are sitting in the forecourt of the health centre supported by Médecins Sans Frontières (MSF) in Kibera South.

"When MSF started working in Lindi village in Kibera, the team visited sick people at home," said Hamida. "My daughter, Hawa's mother, was one of the first patients to receive care from MSF. Unfortunately it was too late: she died two weeks later. Soon afterwards, Hawa started to feel terribly ill. I took her to the MSF centre to be treated."

Hawa is an Aids orphan. There are some 1.4 million of them in Kenya, and they have all lost at least one parent to Aids. At the current rate, their numbers could reach a catastrophic level of two million in a year. Like many others, Hawa is also infected with HIV, transmitted to her by her mother during birth.

Hawa was registered in the MSF programme when she tested positive soon after the death of her mother in 2003. She started antiretroviral therapy three months later.

"I have to take a pill in the mornings and evenings," she said. "In the beginning it was hard because I am not used to taking medicines but it's easier now."

Hamida is Hawa's 'treatment assistant', the person responsible for Hawa sticking to her treatment. This is an indispensable role in the treatment of children. "I love playing ball and hide and seek," said Hawa. "Sometimes I forget to take my medicines when I want to play. My grandmother reminds me."

Hawa is in a support group for children, organised once a month by MSF counsellors in the Gatwekera dispensary.

"I belong to the big children's group. We play, we eat and we talk about HIV/Aids, the medicines and relationships between boys and girls. For the girls, we also talk about periods and what to do with them."

These groups help young people come to terms with their HIV-positive status.

"My friends don't know that I am infected. If I said something at school, they would avoid me. They know that HIV/Aids exists but they think the virus can be transmitted just by talking to someone."

Only her neighbours know about Hawa's status. Recently, one of them forbade her grandson to play with Hawa in case he contracted the virus.

Hamida cares for her granddaughter alone. It is a heavy burden for her.

"I am the only breadwinner in the family," she said. "I do some cleaning, I sell perfumes and so on. Anything I can find to earn a bit of money. But my legs ache now if I work from dawn to dusk. I am 60 years old. If I die, what will happen to my granddaughter? Who will feed her? She must eat correctly - I know how important this is. My other grandchildren can manage, but Hawa? She's a little girl just like others, but she needs special attention."

In the blinding afternoon sunshine, Hawa sets off on her scooter, the lace on her long white dress fluttering behind her.

"I finish primary school next year," she announces shyly, before disappearing into the maze of the slum. Hawa dreams of becoming a doctor. "An HIV/Aids specialist."