According to the 2009 AIDS Epidemic Update, the number of people living with HIV worldwide continued to grow in 2008, reaching an estimated 33.4 million. The total number of people living with the virus in 2008 was more than 20% higher than the number in 2000, and the prevalence was roughly threefold higher than in 1990.

The continuing rise in the population of people living with HIV reflects the combined effects of continued high rates of new HIV infections and the beneficial impact of antiretroviral therapy. As of December 2008, approximately 4 million people in low- and middle-income countries were receiving antiretroviral therapy-a 10-fold increase over five years.

In 2008, an estimated 2.7 million new HIV infections occurred. It is estimated that 2 million deaths due to AIDS-related illnesses occurred worldwide in 2008. The latest epidemiological data indicate that globally the spread of HIV appears to have peaked in  1996, when 3.5 million new HIV infections occurred. In 2008, the estimated number of new HIV infections was approximately 30% lower than at the epidemic's peak 12 years earlier.

This report is divided into separate chapters that summarize epidemiological trends in individual regions. While regional differences remain, several themes are discernible:

• AIDS continues to be a major global health priority;
• There is geographic variation between and within countries and regions;
• The epidemic is evolving;
• There is evidence of successes in HIV prevention;
• Improved access to treatment is having an impact;
• There is increased evidence of risk among key populations.