UNAIDS 2007 AIDS Epidemic Update

11.29.07

UNAIDS issued their 2007 epidemiology report on November 20 providing an overview on the state of the pandemic. The report garnered significant press attention because of the significant change in numbers from the 2006 report. Below are a summary of the report and an explanation of why the numbers changed so dramatically.

Major findings and what they mean for fighting the pandemic

UNAIDS revised the estimate of people living with AIDS from 39.5 million in 2006 to 33.2 million in 2007. This shift is the result of new methodology not of a decline in HIV/AIDS prevalence.

Despite slightly lower figures, HIV/AIDS is still a crisis: The number of people living with HIV globally continues to rise slightly—in 2006 there were an estimated 32.7 million living with HIV/AIDS and in 2007 the number rose to 33.2 million. Globally, this means that every day, 6,800 people are infected and 5,700 die from HIV/AIDS. AIDS is still the single largest cause of death in Africa and the worst public health crisis worldwide.

Africa still bears the brunt of the epidemic:

• 68% of those infected with HIV/AIDS live in Sub-Saharan Africa. Nearly 90% of all HIV positive children (less than 15 years old) live in sub-Saharan Africa.
• 76% of all deaths from HIV/AIDS take place in Africa.
• National adult HIV prevalence exceeded 15% in eight countries in 2005 (Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland, Zambia, and Zimbabwe).

We are getting better at tracking and measuring the shape of the pandemic: UNAIDS has adopted a more sophisticated methodology for tracking the disease. The new figures incorporate more widespread household surveys at the country level and better analysis linking survey data to country wide estimates. The figures also provide more details as to the way the epidemic is distributed across and within countries. As a result, whereas under the old methodology 39.5 million people were estimated to be infected with HIV/AIDS globally, UNAIDS now estimates that in the same year 32.7 million were actually infected. This represents a 17% reduction in the estimated figures. Other changes:

• Under the old methodology, UNAIDS estimated that 2.9 million died in 2006, but new estimates reveal that 2.1 million died.
• Under the old methodology, UNAIDS estimated that 4.3 million were newly infected in 2006, but new estimates reveal that 2.7 million were newly infected.

It is important to not that while we are getting better methodology, these estimates remain just that—estimates. They are not perfect and will likely continue to be adjusted as we get better and better data.

*The above figures are all adjusted using the newly released methodology

The report finds that the number of people contracting AIDS annually and the number of people dying from the disease annually are on the decline while the number of people living with HIV/AIDS is still rising slightly. Because of recent increases in access to treatment, the rate of deaths per year due to AIDS has declined in recent years and remained stable in 2007. Cote d’Ivoire, Kenya and Zimbabwe have all seen downward trends in their national prevalence percentages. HIV prevalence among young pregnant women attending antenatal clinics has declined since 2000/2001 in 11 of 15 most-affected countries. Though impressive findings, the new figures have large margins for error meaning that it’s possible that the conclusion about reversing trends could still be incorrect.

Why and how did UNAIDS change their methodology?

This year, UNAIDS and WHO undertook the most extensive review of HIV/AIDS estimation methodology since 2001. A number of countries, mostly in Sub-Saharan Africa and Asia, have expanded and improved their HIV surveillance systems. In India alone, the number of sentinel surveillance sites increased to more than 1100 in 2006, up from 155 in 1998. Thirty countries in Africa have now conducted national representative population based household surveys, thanks in part to funding from PEPFAR and the Global Fund. The addition of these household surveys greatly enhances the accuracy of our estimates and as more household surveys are conducted, this data will improve even more.

Several new assumptions have been incorporated into the 2007 estimate:

• In countries which have not conducted a national population-based survey, HIV data from antenatal clinic attendees has been adjusted downward. Previously, only the HIV prevalence data from antenatal clinics in rural areas were adjusted.
• The average number of years that people living with HIV are estimated to survive without treatment has been increased from 9 to 11 years.

Approximately 70% of the difference in numbers between this year and last is explained by reductions in prevalence in India (which alone accounts for approximately half of the revisions) and several sub-Saharan African countries, including Nigeria, Mozambique, Zimbabwe, Kenya and Angola. In Kenya and Zimbabwe, there is evidence that the decline is due to a reduction in the number of new infections in part due to a reduction in risky behavior.

Impact on resource needs

UNAIDS issued a global resource needs estimate in September. The resource needs estimate incorporated some of the epidemiological changes described in this brief but not all. Additional changes in the estimated number of people in need of treatment will require additional changes to the resource needs estimate. UNAIDS plans to release a revised estimate by the end of November 2007. We anticipate this report will reveal a 5% decline in the resources needed by 2010 and between a 10-15% decline in the resource estimates for 2015.

Read the Report