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New HIV/AIDS estimates released

By Kristen Jill Kresge

In advance of World AIDS Day, commemorated on December 1, the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) released annually-updated HIV prevalence and incidence figures that help to gauge the scope of the global HIV/AIDS epidemic. According to the 2007 data, there are an estimated 33.2 million individuals worldwide who are living with HIV and of those, 2.5 million individuals were newly infected this year. Also, more than two million deaths over the past year were attributed to HIV/AIDS-related causes, raising the cumulative death toll to 20 million.

TThis year's prevalence figures are significantly lower than in previous years. In 2006, UNAIDS and the WHO estimated that just under 40 million individuals were HIV infected globally, which was also lower than the 2005 estimate. The difference between this year's numbers and those for 2006 is largely attributed to improved efforts to monitor the epidemic and the implementation of better modeling tools, which are used to extrapolate available data from HIV surveillance systems and generate estimates of regional HIV prevalence. Much of this year's drop was attributed to India. In July the Indian government drastically revised the estimated number of individuals in the country who were HIV infected from 5.7 million to 2.5 million. This substantial revision helped push global estimates downward, but other countries lowered their estimates as well, including Angola, Kenya, Nigeria, Mozambique, and Zimbabwe. The UNAIDS/WHO 2007 AIDS epidemic update also attributes lower HIV prevalence in these countries to the success of HIV prevention and treatment programs.

Many of the earlier estimates on the extent of the HIV/AIDS pandemic were based on data collected primarily from pregnant women (see VAX September 2007 Spotlight article, HIV prevalence estimates: Fact or fiction?). This data was easiest to collect because these women were more likely to seek healthcare services. However, this method also tended to overestimate the number of people who were actually infected with HIV since the prevalence was then based mostly on wealthier, sexually active women in urban areas who weren't representative of the country as a whole. Over the years many countries have started conducting household surveys, in which healthcare workers move from house to house counseling and testing individuals for HIV infection, to collect more accurate data. In almost all countries where this method was used, it has resulted in lower prevalence estimates.

UNAIDS and the WHO now also say that the global HIV incidence peaked sometime late in the last decade, when approximately three million people were newly infected with the virus in a single year. Since then, the number of new infections each year has slowly declined, reflecting both the natural course of the global epidemic and the success of HIV prevention efforts, according to the report. Many statisticians and scientists have warned for some time that the UNAIDS/WHO estimates were overblown. But with 2.5 million new HIV infections occurring this year, the battle against AIDS is far from over.

Despite a declining HIV prevalence in some African countries, the continent is still the most severely affected. Sub-Saharan Africa is home to 68% of the world's HIV-infected individuals, and the majority of them are women. Just this year, 1.6 million people in that region died from HIV/AIDS. In other areas, including Eastern Europe and Asia, HIV infection rates continue to rise, though most of the new infections still occur within populations at increased risk of infection, including men who have sex with men, injection-drug users, and sex workers