The report noted that while the epidemic appeared to have stabilized in most parts of the world, the number of people living with HIV continued to grow, reaching 33.4 million by December 2008.

This was partly the result of better access to life-prolonging antiretroviral (ARV) treatment - four million people, or 42 percent of those needing the medication were receiving it by the end of 2008 - but an estimated 2.7 million new HIV infections were added.

"There are clear signs that HIV prevention methods are beginning to make a difference, but we're still not moving fast enough to keep pace with this virus," Paul De Lay, UNAIDS deputy executive director told journalists during a telephonic press briefing from Geneva.

ARV therapy is thought to have saved around 2.9 million lives, contributing to a 10 percent drop in AIDS-related deaths in the past five years, but AIDS still claimed two million lives in 2008, and for every two people who started treatment, five were newly infected.

De Lay warned that the epidemic had changed in the last decade, but prevention responses had not evolved accordingly. For example, Asia's epidemic had mainly been concentrated among injecting drug users, sex workers and their clients, but an increasing number of infections were now occurring among heterosexual couples.

In sub-Saharan Africa - still the most heavily affected area, accounting for 71 percent of all new infections in 2008 - prevention campaigns tended to overlook older heterosexual couples, despite evidence that most new infections in many countries were occurring in this group. In Swaziland, people older than 25 years experienced two-thirds of new infections, yet most prevention programmes targeted younger people.

Although HIV surveillance has become more sophisticated, with more countries conducting household surveys to supplement HIV prevalence data from antenatal clinics, De Lay said there was still a lack of understanding about evolving transmission patterns and the at-risk populations in need of prevention services.

The UNAIDS update noted that although heterosexual intercourse was the primary mode of HIV transmission in sub-Saharan Africa, recent evidence showed that "epidemics in the region are much more varied than previously understood", with a considerable number of new infections occurring among men who have sex with men and injecting drug users.

The report urged countries to do a better job of matching national AIDS strategies to individual epidemics, and De Lay agreed that "We need to use the resources available much more effectively, particularly in these times of economic crisis."

Nevertheless, the report recorded progress in several areas: prevention of mother-to-child HIV transmission (PMTCT) services reached 45 percent of HIV-positive pregnant women in 2008, averting an estimated 200,000 infant infections since 2001; in several high-prevalence countries the number of children orphaned by HIV/AIDS dropped because parents on ARV treatment were living longer.

Dr Teguest Guerma, acting director of the World Health Organization's HIV/AIDS department, also speaking from Geneva, emphasized that international assistance to the global AIDS response had helped save lives, and that there was a "moral imperative" to extend and strengthen that response.

UNAIDS Outlook 2010, a companion report also released on 24 November, noted that AIDS funding reached a record high of US$15.6 billion in 2008, with international assistance accounting for 55 percent, and that most of the money had gone to sub-Saharan African countries.

Whether these funding levels will be sustained in the current economic crisis is unclear, but Outlook 2010 noted that many countries were already experiencing funding cuts for treatment and prevention services.

"We cannot afford to let the economic crisis paralyse us," said the report, quoting Michel Sidibe, executive director of UNAIDS. "Not when the AIDS response is showing results."

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