This does not explain why the article in question included the following paragraph:
In a study in the journal PLoS Medicine, British researchers said Zimbabwe's epidemic was one of the biggest in the world until the rate of people infected with HIV almost halved, from 29 percent of the population in 1997 to 16 percent in 2007.Percentage of the population becoming infected every day? Every week? Every year? Or perhaps just the percentage of the population who are HIV positive. In which case, the situation is not only wholly different but is not, in fact, something to celebrate. The number of people with HIV - and unless the population changes dramatically (for e.g. through genocide), the percentage of the population with HIV - can only increase. People don't stop being HIV positive. The only way that number goes down, as it apparently has in Zimbabwe, is mass migration of HIV positive people (which we hope hasn't happened on that scale) or people who are HIV positive dying. The decrease in the percentage of the population that is HIV positive in a country is encouraging only if you first accept that the initial decrease is because people have died (or moved) and then get excited that those cases of HIV infection haven't immediately been replaced by new infections.
The article also gives no indication of the change in infection rates, the measure used -Antenatal surveys? Voluntary testing? Something else? - or, really, the findings of the study into why infection rates have dropped. I understand that reporters are not health experts but if you're going to write articles about Southern Africa, a basic grasp of the terminology and concepts around the epidemic that is such a large fact of life there should be the absolute minimum requirement.