"There's no way that we're going to win this battle without more openness

Peter Piot UN Aids executive director

Peter Piot, talking to a gathering of African presidents in South Africa, said this was a sign that the continent was "at the turning point" in the fight against the epidemic.

In the past, a reluctance to talk about Aids and sexual practices has been considered a block to progress among African governments.

But Mr Piot encouraged his audience to keep talking.

"There's no way that we're going to win this battle," he said, "without more openness about the issue and about sex and more effort against the stigma that's associated with HIV."

Nkosi Johnson helped a lot of people realise the size of the problem

Mr Piot was speaking at a meeting of the World Economic Forum in Durban, where it is being argued that Aids is not just a health issue but it is also threat to countries' development.

Uganda and Senegal are often cited as countries where the openness to discussion about Aids and sex has made a difference as infection rates appear to be falling.

Slow change

In South Africa, however, the anti-Aids campaign seems to have made little progress so far. One in nine South Africans are thought to be HIV positive.

Aids activists have criticised President Thabo Mbeki for failing to give clear leadership in the fight against the disease.

They have accused him of spreading confusion about how HIV and Aids are transmitted.

Nkosi Johnson, the 12-year old boy who died of Aids last week, has been acclaimed as helping South Africans recognise the scale of the problem in the country.