It was a warm sultry day last spring when I heard about a small 12-year-old girl who had been raped and consequently infected with the HIV/Aids virus. I was in South Africa with Elton John and David Furnish to see at the most basic grassroots level how their Aids charity works.

This girl's mother had been physically abused by her partner, but then he allowed her daughter to get into a car with a driver she did not even know, supposedly to take her home – she ended up being raped. Psychologically as well as physically she was hurt, eventually becoming withdrawn and sick from HIV.

I heard this and other shocking stories from Primrose Thetyane, an auxiliary social worker at Mosaic's satellite office at Score Centre in Harare, Khayelitsha. There they try to change what may seem like a potential death sentence into a way to survive by giving care, hope, medication and counselling. A key treatment was something called a PEP (post exposure prophylaxis), which prevents transmission of HIV from rapist to victim if administered in time.

It struck me how extraordinarily varied were the HIV sufferers who were helped by the foundation. A gay shelter allowed intimidated sick men to feel protected and secure and no longer in fear of the consequences of their sexuality. The Health4Men programme had been launched in Cape Town 18 months ago, and is the first clinic specifically for men who have had sex with other men that operates within the public health system in South Africa. Possibly the only one in Africa, as most African countries do not accept homosexuality and in several it is a capital offence. What surprised me was that there was a plaque on the wall indicating that the American government under George W Bush had also helped fund the clinic. I was told he had signed off on the funding without quite realising it would end up helping gay men.

There were many inspiring individual stories of suffering which I heard that resonated in my mind for a long time afterwards. Each was like a fresh wound. So many suffering and so much needed to do to help. We drove from a shelter to a medical centre, where, as always, the number of people in need of help exceeded the amount of money and human care available. Heartbreaking was the innocence and acceptance of their situation by infected children, scared and their lives potentially shortened.

I had been given a special chance to see projects helped by the £200m that Elton John has raised for his HIV/Aids charity, especially in Africa, where 27.7 million of the 33 million people living with HIV/Aids live. South Africa has one of the highest numbers of children under 15 living with the virus; estimates range from 180,000 to 280,000. It is shocking and sobering to think that there are 13 million orphans in Africa. I now understand better why Elton has spent a thirdof his life trying to help.