Researchers have reported the first decline in HIV prevalence in southern Africa, attributing the drop, recorded in eastern Zimbabwe, to changes in sexual behaviour.
In a paper published today (3 February) in Science, Simon Gregson of Imperial College London, United Kingdom, and colleagues report that the prevalence of HIV in the study area fell from 23 per cent of the population in 1998 to 20.5 per cent in 2003.
They say a well-educated population, good risk communication, and a fear of dying of AIDS are likely to have influenced these changes.
Prevalence declined most among young and educated people, including drops of 23 per cent among men aged 17-29 and 49 per cent among women aged 15-24.
The study found evidence that men and women were having their first sexual activity later, and fewer casual relationships.
It adds that there was no evidence for increased condom use with regular partners, but that for men, "consistent condom use in casual partnerships lessened the risk of HIV infection".
Gregson's team warns that the results should be interpreted with caution, as migration and the deaths of HIV-infected people could partly explain the decline.
Zimbabwe joins Thailand and Uganda on the shortlist of countries that have seen substantial decreases in HIV prevalence, say Richard Hayes and Helen Weiss of the UK-based London School of Tropical Medicine and Hygiene in an accompanying commentary in Science.
They say there is also growing evidence of declines in Burkina Faso, Cambodia, Haiti and Kenya (see HIV rates fall in parts of Africa and Caribbean).
"However, the overall picture in sub-Saharan Africa is one in which most countries now have 'stable' epidemics, where AIDS-related mortality is matched by the rate of new infections," add Hayes and Weiss. "And in some southern African countries, the prevalence of HIV continues to rise."
Reference: Science 311, 664 (2006)