Measuring the impact of the global response to the AIDS epidemic: challenges and future directions.

OBJECTIVES: In the Declaration of Commitment of the 2001 United Nations General Assembly Special Session on AIDS, all Member States agreed to a series of actions to address HIV. This article examines the availability of data to measure progress toward reducing HIV incidence and AIDS mortality and discusses the extent to which changes can be attributed to programs. METHODS: Lacking a method to directly measure HIV incidence, trends in HIV prevalence among 15-year to 24-year olds and groups with high-risk behaviors are used as a proxy measure for incidence trends among adults in generalized and concentrated/low-level epidemics, respectively. Although there is limited empirical data on trends in new infections among children, progress in the treatment area is tracked through indicators for the percentage of people who remain on antiretroviral treatment 12 months after initiation and the coverage of antiretroviral treatment. Successive iterations of epidemiological models using surveillance data from pregnant women and groups with high-risk behavior and data from national household surveys, demographic data and epidemiological assumptions have produced increasingly robust estimates of HIV prevalence, incidence and mortality. RESULTS: Globally, incidence has decreased among adults (accompanied by evidence of changes in behavior in several countries) and children over the past decade. The decline in AIDS mortality is more recent. On the basis of the underlying logical framework and mathematical models, it is concluded that programs have contributed to a reduction in HIV incidence and AIDS mortality. CONCLUSIONS: More data are needed to reliably inform trends in HIV incidence and AIDS mortality in many countries to allow an assessment of progress against national and global targets. In addition, impact evaluation studies are needed to assess the relationship between changes in incidence and mortality and the HIV response and to determine the extent to which these changes can be attributed to specific programmatic interventions.

The epidemiology of HIV infection among young people aged 15-24 years in southern Africa.

OBJECTIVES: To investigate epidemiological patterns and trends of HIV infection and sexual behaviour among young people aged 15-24 years in the nine countries in southern Africa most affected by the HIV epidemic. METHODS: Data on HIV prevalence among young people in the general population were obtained from national population-based surveys conducted between 2000 and 2007, whereas data on sexual behaviour were obtained from repeat surveys between 1994 and 2007. Linear or exponential regression was used to analyse HIV prevalence trends among young women attending antenatal clinics in recent years. RESULTS: Patterns of HIV infection among young people are similar across the countries included in this analysis. The prevalence of HIV increases after the age of 15 years, more rapidly among women than among men, reaching a peak among women in their twenties and men in their thirties. Between 2000 and 2007 the prevalence of HIV among antenatal clinic attendees was constant in Mozambique and South Africa and declining in Lesotho, Namibia, Swaziland, Zambia, Botswana, Malawi and Zimbabwe, but only reached statistical significance (P < 0.05) in the last three. Changes towards safer sexual behaviour were observed over time among young men and women in the general population in this region. CONCLUSION: Sexual behaviour changes among young people are encouraging and are associated with declines in HIV prevalence among young antenatal clinic attendees over time. More research is needed to understand the recent changes and the very high prevalence among young women in this region. Interventions aimed at reducing risky behaviour need to be supported and expanded while incorporating new approaches to prevention.

The global impact of scaling up HIV/AIDS prevention programs in low- and middle-income countries.

A strong, global commitment to expanded prevention programs targeted at sexual transmission and transmission among injecting drug users, started now, could avert 28 million new HIV infections between 2005 and 2015. This figure is more than half of the new infections that might otherwise occur during that period in 125 low- and middle-income countries. Although preventing these new infections would require investing about U.S.$122 billion over this period, it would reduce future needs for treatment and care. Our analysis suggests that it will cost about U.S.$3900 to prevent each new infection, but that this will produce a savings of U.S.$4700 in forgone treatment and care costs. Thus, greater spending on prevention now would not only prevent more than half the new infections that would occur from 2005 to 2015 but would actually produce a net financial saving as future costs for treatment and care are averted.

Monitoring the scale-up of antiretroviral therapy programmes: methods to estimate coverage.

This paper reviews the data sources and methods used to estimate the number of people on, and coverage of, antiretroviral therapy (ART) programmes in low- and middle-income countries and to monitor the progress towards the "3 by 5" target set by WHO and UNAIDS. We include a review of the data sources used to estimate the coverage of ART programmes as well as the efforts made to avoid double counting and over-reporting. The methods used to estimate the number of people in need of ART are described and expanded with estimates of treatment needs for children, both for ART and for cotrimoxazole prophylaxis. An estimated 6.5 million people were in need of treatment in low- and middle-income countries by the end of 2004, including 660,000 children under age 15 years. The mid-2005 estimate of 970,000 people receiving ART in low- and middle-income countries (with an uncertainty range 840,000-1,100,000) corresponds to a coverage of 15% of people in need of treatment.

Integrating HIV prevention and treatment: from slogans to impact.

BACKGROUND: Through major efforts to reduce costs and expand access to antiretroviral therapy worldwide, widespread delivery of effective treatment to people living with HIV/AIDS is now conceivable even in severely resource-constrained settings. However, the potential epidemiologic impact of treatment in the context of a broader strategy for HIV/AIDS control has not yet been examined. In this paper, we quantify the opportunities and potential risks of large-scale treatment roll-out. METHODS AND FINDINGS: We used an epidemiologic model of HIV/AIDS, calibrated to sub-Saharan Africa, to investigate a range of possible positive and negative health outcomes under alternative scenarios that reflect varying implementation of prevention and treatment. In baseline projections, reflecting "business as usual," the numbers of new infections and AIDS deaths are expected to continue rising. In two scenarios representing treatment-centered strategies, with different assumptions about the impact of treatment on transmissibility and behavior, the change in the total number of new infections through 2020 ranges from a 10% increase to a 6% reduction, while the number of AIDS deaths through 2020 declines by 9% to 13%. A prevention-centered strategy provides greater reductions in incidence (36%) and mortality reductions similar to those of the treatment-centered scenarios by 2020, but more modest mortality benefits over the next 5 to 10 years. If treatment enhances prevention in a combined response, the expected benefits are substantial-29 million averted infections (55%) and 10 million averted deaths (27%) through the year 2020. However, if a narrow focus on treatment scale-up leads to reduced effectiveness of prevention efforts, the benefits of a combined response are considerably smaller-9 million averted infections (17%) and 6 million averted deaths (16%). Combining treatment with effective prevention efforts could reduce the resource needs for treatment dramatically in the long term. In the various scenarios the numbers of people being treated in 2020 ranges from 9.2 million in a treatment-only scenario with mixed effects, to 4.2 million in a combined response scenario with positive treatment-prevention synergies. CONCLUSIONS: These analyses demonstrate the importance of integrating expanded care activities with prevention activities if there are to be long-term reductions in the number of new HIV infections and significant declines in AIDS mortality. Treatment can enable more effective prevention, and prevention makes treatment affordable. Sustained progress in the global fight against HIV/AIDS will be attained only through a comprehensive response.

Estimating the global burden of HIV/AIDS: what do we really know about the HIV pandemic?

The validity of UNAIDS/WHO estimates of the burden of HIV/AIDS is rightly questioned by politicians, scientists, and activists-especially since the 2003 estimates to be released in July, 2004, will show substantial drops in the burden of HIV/AIDS in several countries, and increases in others. However, the estimates are based on an explicit attempt to meet criteria we believe should guide the generation of international morbidity and mortality figures. These criteria extend beyond the quality of the input data to include features of the estimation process such as transparency and participation. The 2003 estimates now include plausible ranges for estimates rather than a single best estimate. This reduces the chance that insignificant differences in estimates from different sources are given importance. Here, we describe the levels of uncertainty associated with the UNAIDS/WHO estimates of HIV/AIDS. We explain the reason for moving to the use of plausibility bounds, the factors that determine the width of the bounds, and the implications for policy makers and programme managers.

Methods and procedures for estimating HIV/AIDS and its impact: the UNAIDS/WHO estimates for the end of 2001.

BACKGROUND: The Joint United Nations Programme on HIV and AIDS (UNAIDS) and the World Health Organization (WHO) have produced country-specific estimates of HIV/AIDS biannually since 1997. These estimates are a primary source of information about the extent and spread of the HIV/AIDS epidemic and its impact. The importance of having comparable country-specific estimates of HIV/AIDS is growing as estimates are used to determine how international resources to fight HIV/AIDS will be allocated to countries. OBJECTIVES: This paper describes the procedures and process used to make the 2001 round of UNAIDS/WHO estimates of HIV/AIDS. The paper focuses on the different approaches used to make estimates of prevalence in countries with generalized and low-level and concentrated epidemics as well as on new curve-fitting software that was developed to produce epidemic curves for each country. In addition, it presents the assumptions used (e.g. survival from infection to death, the rate of mother-to-child transmission) that are required to derive estimates of incidence and mortality in adults, as well as prevalence, incidence and mortality in children. CONCLUSION: The paper describes the general process by which the estimation and modelling procedures have been refined and improved over time. The paper also discusses the limitations and weaknesses of the procedures and the data used to make the estimates, and suggests areas where further improvements need to be made.

Can we reverse the HIV/AIDS pandemic with an expanded response?

HIV/AIDS has reached pandemic proportions, and is one of the leading causes of death worldwide. In 2001, the Declaration of Commitment on HIV/AIDS set out several aims with respect to reducing the effect and spread of HIV/AIDS, and an expanded response in low-income and middle-income countries was initiated. Here we examine the potential effect of the expanded global response based on analyses of epidemiological data, of mathematical models of HIV-1 transmission, and a review of the impact of prevention interventions on risk behaviours. Analyses suggest that if the successes achieved in some countries in prevention of transmission can be expanded to a global scale by 2005, about 29 million new infections could be prevented by 2010.