A new analysis of the Aids epidemic in South Africa suggests that fewer people are becoming infected with HIV than in previous years.
One in 10 South Africans is HIV positive
The research also predicts that the total number of HIV-positive people in South Africa will remain constant for the foreseeable future.
About 5m South Africans carry the Aids virus - more than in any other country.
The researchers say Aids remain a "huge burden" in the country.
Research from ante-natal clinics shows that the proportion of young women carrying the Aids virus has declined over the last five years.
Scientists have now combined that finding with information from a recent nationwide survey, and put the data into a computer programme which aims to model the epidemic.
The results were published in the African Journal of Aids Research.
They suggest that the annual rate of new infections has declined substantially, from 4.1% of the population aged 15-49 in 1997 to 1.7% in 2002.
One of the researchers, Dr Thomas Rehle, says that is partly because young people are paying more attention to safe sex education.
"Well, it looks like people more and more get the message. And particularly among the young groups, it looks like it gets better and better absorbed."
But BBC science correspondent Richard Black says the epidemic is certainly far from over.
In the immediate future, the proportion of the adult population infected with HIV will stay roughly constant, the researchers say; the average life expectancy will continue to fall for around 10 years.
The projections made by this research team are considerably lower than previous estimates, and the scientists acknowledge there are uncertainties in their figures.
But they emphasise their analysis does not mean that the scale of the AIDS problem has been exaggerated.