By Peter Biles
BBC Southern Africa correspondent
The South African government says that for the first time, there may be signs of a reduction in the prevalence of HIV, the virus that causes Aids.
The results are being greeted with cautious optimism
A government survey found that HIV prevalence among pregnant women across the country had dropped by one percentage point.
South Africa has one of the world's worst infection rates, with an estimated 5.5m people HIV-positive.
Last year 29.1% of pregnant women were HIV-positive compared to 30.2% in 2005.
The Department of Health says this suggests that for the first time, the epidemic in South Africa may be beginning a downward trend, but needs to be observed carefully in the next few years to confirm this.
"It's hard to call it a decline, but the good news is that it's not getting worse," one public health official said.
"The situation might be starting to stabilise."
The decline is said to be mainly among people under the age of 20, which epidemiologist David Bourne of the University of Cape Town described as an "encouraging" sign.
Health Minister Manto Tshabalala-Msimang also welcomed the results of the survey.
"The decline in the under 20s from 15.9% in 2005 to 13.7% in 2006 in particular suggests a possible reduction in new infections in the population and we hope to sustain this trend," the minister said.
It is too early to say whether a turning point has been reached in fighting HIV and AIDS.
Dr Tshabalala-Msimang confirmed that more than 280,000 people were on anti-retroviral (ARV) treatment, which suppresses the symptoms of HIV, by the end of March this year.
But she said reports that the next generation of ARV drugs might cost five times as much as they do at present, was worrying for developing countries with limited resources.
"The reduction of the prices of medicines and other essential commodities remains a very critical area of intervention," the minister said.