A story long in the making went public today: The UN has revised its estimates for HIV prevalence around the world.
From the full report [pdf file]:
In 2007, advances in the methodology of estimations of HIV epidemics applied to an expanded range of country data have resulted in substantial changes in estimates of numbers of persons living with HIV worldwide. However the qualitative interpretation of the severity and implications of the pandemic has altered little. The estimated number of persons living with HIV worldwide in 2007 was 33.2 million [30.6-36.1 million], a reduction of 16% compared with the estimate published in 2006 (39.5 million [34.7-47.1 million]). The single biggest reason for this reduction was the intensive exercise to assess India’s HIV epidemic, which resulted in a major revision of that country’s estimates. Important revisions of estimates elsewhere, particularly in sub-Saharan Africa, also contributed. Of the total difference in the estimates published in 2006 and 2007, 70% are due to changes in six countries: Angola, India, Kenya, Mozambique, Nigeria, and Zimbabwe. In both Kenya and Zimbabwe, there is increasing evidence that a proportion of the declines is due to a reduction of the number of new infections which is in part due to a reduction in risky behaviours.
Because estimates of new HIV infections and HIV-associated deaths are derived through mathematical models applied to HIV prevalence estimates, new estimates of HIV incidence and mortality in 2007 also differ substantially from earlier assessments. It is emphasized that these differences between estimates published in 2006 and those published in 2007 result largely from refinements in methodology, rather than trends in the pandemic itself...
Global HIV prevalence—the percentage of the world’s adult population living with HIV—has been estimated to be level since 2001. Downward trends in HIV prevalence are occurring in a number of countries, where prevention efforts aimed at reducing new HIV infections since 2000 and 2001 are showing results. In most of sub-Saharan Africa, national HIV prevalence has either stabilized or is showing signs of a decline. Côte d’Ivoire, Kenya and Zimbabwe have all seen declines in national prevalence, continuing earlier trends. In South-East Asia, the epidemics in Cambodia, Myanmar and Thailand all show declines in HIV prevalence.