AIDS statistics revised by WHO in 2007

Nov 21 2007

New data show global HIV prevalence - the percentage of people living with HIV - has levelled off and that the number of new infections has fallen, in part as a result of the impact of HIV programmes.

However, in 2007 33.2 million [30.6 - 36.1 million] people were estimated to be living with HIV, 2.5 million [1.8 - 4.1 million] people became newly infected and 2.1 million [1.9 - 2.4 million] people died of AIDS.

There were an estimated 1.7 million [1.4 - 2.4 million] new HIV infections in sub-Saharan Africa in 2007—a significant reduction since 2001. However, the region remains most severely affected. An estimated 22.5 million [20.9 - 24.3 million] people living with HIV, or 68% of the global total, are in sub-Saharan Africa. Eight countries in this region now account for almost one-third of all new HIV infections and AIDS deaths globally.

Since 2001, when the United Nations Declaration of Commitment on HIV/AIDS was signed, the number of people living with HIV in Eastern Europe and Central Asia has increased by more than 150% from 630 000 [490 000 - 1.1 million] to 1.6 million [1.2 - 2.1 million] in 2007. In Asia, the estimated number of people living with HIV in Viet Nam has more than doubled between 2000 and 2005 and Indonesia has the fastest growing epidemic.

These findings were released by the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) in the report 2007 AIDS Epidemic Update.

The new report reflects improved and expanded epidemiological data and analyses that present a better understanding of the global epidemic. These new data and advances in methodology have resulted in substantial revisions from previous estimates.

While the global prevalence of HIV infection—the percentage of people infected with HIV— has levelled off, the total number of people living with HIV is increasing because of ongoing acquisition of HIV infection, combined with longer survival times, in a continuously growing general population.

Global HIV incidence—the number of new HIV infections per year—is now estimated to have peaked in the late 1990s at over 3 million [2.4 - 5.1 million] new infections per year, and is estimated in 2007 to be 2.5 million [1.8 - 4.1 million] new infections, an average of more than 6 800 new infections each day. This reflects natural trends in the epidemic, as well as the result of HIV prevention efforts.

The number of people dying from AIDS-related illnesses has declined in the last two years, due in part to the life prolonging effects of antiretroviral therapy. AIDS is among the leading causes of death globally and remains the primary cause of death in Africa.

“These improved data present us with a clearer picture of the AIDS epidemic, one that reveals both challenges and opportunities,” said UNAIDS Executive Director Dr Peter Piot. “Unquestionably, we are beginning to see a return on investment—new HIV infections and mortality are declining and the prevalence of HIV levelling. But with more than 6 800 new infections and over 5 700 deaths each day due to AIDS we must expand our efforts in order to significantly reduce the impact of AIDS worldwide.”

UNAIDS, WHO and the Reference Group on Estimates, Modelling and Projections have recently undertaken the most comprehensive review of their methodologies and monitoring systems since 2001. The epidemic estimates presented in this year's report reflect improvements in country data collection and analysis, as well as a better understanding of the natural history and distribution of HIV infection. This information is vital in helping countries understand their epidemics and respond to them more effectively.

UNAIDS and WHO are now working with better information from many more countries. In the past few years a number of countries, most notably in sub-Saharan Africa and Asia, have expanded and improved their HIV surveillance systems, conducting new, more accurate studies that provide more precise information about HIV prevalence than earlier studies. In addition, 30 countries mostly in Africa have conducted national representative population-based household surveys. These have also informed adjustments for other countries with similar epidemics that have not conducted these surveys. New assumptions have also been made as a result of a better understanding of the natural history of untreated HIV infection.

The current estimate of 33.2 million [30.6 - 36.1 million] people living with HIV replaces the 2006 estimate of 39.5 million [24.5 - 47.1 million]. Applying the improved methodology retrospectively to the 2006 data, the 2007 report revises that figure, now estimating that in 2006 there were 32.7 million [30.2 - 35.3 million] people living with HIV. The single biggest reason for the reduction in global HIV prevalence figures in the past year was the recent revision of estimates in India after an intensive reassessment of the epidemic in that country. The revised estimates for India, combined with important revisions of estimates in five sub- Saharan African countries (Angola, Kenya, Mozambique, Nigeria, and Zimbabwe) account for 70% of the reduction in HIV prevalence as compared to 2006 estimates.

"Reliable public health data are the essential foundation for an effective response to HIV/AIDS", said WHO's HIV/AIDS Director Dr Kevin De Cock. "While these new estimates are of better quality than those of the past, we need to continue investing more in all countries and all aspects of strategic information relating to health."

"The data for measuring the HIV epidemic used by UNAIDS/WHO has considerably expanded and improved in recent years,” said Ron Brookmeyer, Professor of Biostatistics and Chair of the Master of Public Health Program, The Johns Hopkins Bloomberg School of Public Health. “Nevertheless, there is a need to further improve the representativeness of the underlying data. There is a need to expand disease surveillance systems to better track the sub-epidemics in risk populations within each country."

"More accurate estimates and trends will ultimately lead to improvements in the design and evaluation of prevention programmes," added Professor Brookmeyer, who was also the Chair of the Independent Review Panel at the recent International Consultation on epidemiological estimates convened by UNAIDS and WHO.

UNAIDS and WHO will continue to update their methodology as new data becomes available from research studies and surveillance data from countries.

HIV prevalence among young pregnant women (15 - 24) attending antenatal clinics has declined since 2000/2001 in 11 of the15 most-affected countries. Preliminary data also show favourable changes in risk behaviour among young people in a number of countries, (Botswana, Cameroon, Chad, Haiti, Kenya, Malawi, Togo, Zambia, and Zimbabwe). These trends suggest that prevention efforts are having an impact in several of the most affected countries.

In sub-Saharan Africa, continued treatment scale-up and HIV prevention efforts are also bringing results in some countries, but mortality from AIDS remains high in Africa due to the extensive unmet treatment need. Cote d'Ivoire, Kenya and Zimbabwe, among others, have all seen downward trends in their national prevalence. Beyond sub-Saharan Africa, declines in new HIV infections have also occurred in South and South-East Asia, notably in Cambodia, Myanmar and Thailand.

There is a need to adapt and revive HIV prevention efforts as some countries are seeing a reversal of declining trends. Burundi's declining trend from the late 1990's did not continue beyond 2005 and HIV prevalence started to increase again at most surveillance sites. Despite achievements in reversing the epidemic in Thailand, HIV prevalence is rising among men who have sex with men and has remained high among injecting drug users over the past 15 years, ranging between 30% to 50%.

UNAIDS and WHO officials point out that the new estimates do not change the need for immediate action and increased funding to scale up towards universal access to HIV prevention, treatment, care and support services.