Producing HIV estimates: from global advocacy to country planning and impact measurement.

BACKGROUND: The development of global HIV estimates has been critical for understanding, advocating for and funding the HIV response. The process of generating HIV estimates has been cited as the gold standard for public health estimates. OBJECTIVE: This paper provides important lessons from an international scientific collaboration and provides a useful model for those producing public health estimates in other fields. DESIGN: Through the compilation and review of published journal articles, United Nations reports, other documents and personal experience we compiled historical information about the estimates and identified potential lessons for other public health estimation efforts. RESULTS: Through the development of core partnerships with country teams, implementers, demographers, mathematicians, epidemiologists and international organizations, UNAIDS has led a process to develop the capacity of country teams to produce internationally comparable HIV estimates. The guidance provided by these experts has led to refinements in the estimated numbers of people living with HIV, new HIV infections and AIDS-related deaths over the past 20 years. A number of important updates to the methods since 1997 resulted in fluctuations in the estimated levels, trends and impact of HIV. The largest correction occurred between the 2005 and 2007 rounds with the additions of household survey data into the models. In 2001 the UNAIDS models at that time estimated there were 40 million people living with HIV. In 2016, improved models estimate there were 30 million (27.6-32.7 million) people living with HIV in 2001. CONCLUSIONS: Country ownership of the estimation tools has allowed for additional uses of the results than had the results been produced by researchers or a team in Geneva. Guidance from a reference group and input from country teams have led to critical improvements in the models over time. Those changes have improved countries' and stakeholders' understanding of the HIV epidemic.

Increasing trends in HIV prevalence among people aged 50 years and older: evidence from estimates and survey data.

OBJECTIVE: To present the most recent 2013 UNAIDS estimates of HIV prevalence among people aged 50 years and older, and to validate these estimates using data from national household surveys. DESIGN: Modelled estimates of HIV prevalence were validated against nationally representative household survey measures of HIV prevalence. METHODS: The UNAIDS 2013 HIV estimates were used to compute HIV prevalence and number of people living with HIV aged 50 years and older. Sex-specific HIV-prevalence rates by the 5-year age group were calculated from nationally representative household surveys conducted between 2003 and 2013, and were compared to prevalence rates from the modelled estimates. The ratios (Spectrum/Survey) of the prevalence rates from the two sources were analysed. RESULTS: In 2013, an estimated 4.2 million (4.0-4.5 million) people aged 50 years and older were living with HIV. The global HIV prevalence among older individuals more than doubled in almost all the 5-year age groups since 1995. There was a relatively good agreement between the modelled HIV-prevalence rates and the survey-based rates among men and women aged 50-54 years (0.90 and 1.00 median ratio, respectively), whereas for 55-59 year-olds, the differences were more notable (ratios of 0.63 for men and 0.90 for women). CONCLUSION: Both data sources suggest HIV-prevalence rates among people aged over 50 have increased steadily in the recent years. Care and treatment services need to address the specific needs of older people living with HIV. Action is needed to incorporate older age groups into HIV surveillance systems.

Estimates of the number of people living with HIV in Italy.

Objective. To estimate the HIV prevalence and the number of people living with HIV (PLHIV) in Italy with a projection for 2020. Methods. Two methods elaborated by Joint United Nations Programme on HIV/AIDS (UNAIDS) were used: Estimate and Projection Package and Spectrum. Results. A total of 123,000 (115,000-145,000) individuals aged 15 or more were estimated to be living with HIV in Italy at the end of 2012 and the estimated HIV prevalence was 0.28 (0.24-0.32) per 100 residents aged 15 or more. In 2012, the estimated number of new HIV infections among adults was 3,000 (2,700-4,000), and the number of adults in need for ART was 93,000 (80,000-110,000). The projection estimates that 130,000 (110,000-150,000) adults will live with HIV/AIDS in 2020 in Italy. Conclusion. Estimates of PLHIV in Italy stress the high number of PLHIV in need of care and treatment, as well as the need for more information and prevention campaigns.

What will it take to achieve virtual elimination of mother-to-child transmission of HIV? An assessment of current progress and future needs.

BACKGROUND: The number of HIV-positive pregnant women receiving antiretroviral drugs (ARVs) to prevent mother-to-child transmission (MTCT) of HIV has increased rapidly. OBJECTIVE: To estimate the reduction in new child HIV infections resulting from prevention of MTCT (PMTCT) over the past decade. To project the potential impact of implementing the new WHO PMTCT guidelines between 2010 and 2015 and consider the efforts required to virtually eliminate MTCT, defined as <5% transmission of HIV from mother to child, or 90% reduction of infections among young children by 2015. METHODS: Data from 25 countries with the largest numbers of HIV-positive pregnant women were used to create five scenarios to evaluate different PMTCT interventions. A demographic model, Spectrum, was used to estimate new child HIV infections as a measure of the impact of interventions. RESULTS: Between 2000 and 2009 there was a 24% reduction in the estimated annual number of new child infections in the 25 countries, of which about one-third occurred in 2009 alone. If these countries implement the new WHO PMTCT recommendations between 2010 and 2015, and provide more effective ARV prophylaxis or treatment to 90% of HIV-positive pregnant women, 1 million new child infections could be averted by 2015. Reducing HIV incidence in reproductive age women, eliminating the current unmet need for family planning and limiting the duration of breastfeeding to 12 months (with ARV prophylaxis) could avert an additional 264 000 infections, resulting in a total reduction of 79% of annual new child infections between 2009 and 2015, approaching but still missing the goal of virtual elimination of MTCT. DISCUSSION: To achieve virtual elimination of new child infections PMTCT programmes must achieve high coverage of more effective ARV interventions and safer infant feeding practices. In addition, a comprehensive approach including meeting unmet family planning needs and reducing new HIV infections among reproductive age women will be required.

Under-5 mortality due to HIV: regional levels and 1990-2009 trends.

BACKGROUND: Since at least the late 1990s, HIV has been viewed as a major threat to efforts by countries to reduce under-5 mortality. Previous work has documented increased under-5 mortality due to HIV from 1990 to 1999 in Africa. The current analysis presents estimates and trends in under-5 mortality due to HIV in low- and middle-income countries by region up to 2009. METHODS: The analyses are based on the national models of HIV and AIDS produced by country teams in coordination with UNAIDS and its partners for the years 1990-2009. These models produce a time series of estimates of HIV-related mortality as well as overall mortality in children aged <5 years. RESULTS AND CONCLUSION: These analyses indicate that, in 2009, HIV accounted for roughly 2.1% (1.2-3.0%) of under-5 deaths in low- and middle-income countries and 3.6% (2.0-5.0%) in sub-Saharan Africa. The percentage of under-5 deaths due to HIV has been falling in the last decade--for example, from 2.6% (1.6-3.5%) in 2000 to 2.1% (1.2-3.0%) in 2009 in low- and middle-income countries and from 5.4% (3.3-7.3%) in 2000 to 3.6% (2.0-5.0%) in 2009 in sub-Saharan Africa. This fall in the percentage of under-5 deaths due to HIV has been driven by a combination of factors including scale-up of prevention of mother-to-child transmission programmes and treatment for pregnant women and children, as well as a decrease in the prevalence of HIV among pregnant women.

Antiretroviral therapy needs: the effect of changing global guidelines.

BACKGROUND: In 2010 the WHO issued a revision of the guidelines on antiretroviral therapy (ART) for HIV infection in adults and adolescents. The recommendations included earlier diagnosis and treatment of HIV in the interest of a longer and healthier life. The current analysis explores the impact on the estimates of treatment needs of the new criteria for initiating ART compared with the previous guidelines. METHODS: The analyses are based on the national models of HIV estimates for the years 1990-2009. These models produce time series estimates of ART treatment need and HIV-related mortality. The ART need estimates based on ART eligibility criteria promoted by the 2010 WHO guidelines were compared with the need estimates based on the 2006 WHO guidelines. RESULTS: With the 2010 eligibility criteria, the proportion of people living with HIV currently in need of ART is estimated to increase from 34% to 49%. Globally, the need increases from 11.4 million (10.2-12.5 million) to 16.2 million (14.8-17.1 million). Regional differences include 7.4 million (6.4-8.4 million) to 10.6 million (9.7-11.5 million) in sub-Saharan Africa, 1.6 million (1.3-1.7 million) to 2.4 million (2.1-2.5 million) in Asia and 710 000 (610 000-780 000) to 950 000 (810 000-1.0 million) in Latin America and the Caribbean. CONCLUSIONS: When adopting the new recommendations, countries have to adapt their planning process in order to accelerate access to life saving drugs to those in need. These recommendations have a significant impact on resource needs. In addition to improving and prolonging the lives of the infected individuals, it will have the expected benefit of reducing HIV transmission and the future HIV/AIDS burden.

Estimating the impact of antiretroviral therapy: regional and global estimates of life-years gained among adults.

OBJECTIVE: An estimated 4.9 million adults received antiretroviral therapy (ART) in low and middle income countries in 2009. A further estimated 700 000 adults received ART in high-income countries. The impact of providing ART is not often quantifiable due to limited monitoring systems. One measure, life-years gained, provides a standardised measure that shows the survival impact of ART on the population while controlling for variations in underlying survival. Measuring life-years gained allows a comparison of the impact of ART between regions. METHODS: Using the Spectrum computer package, two different scenarios were created for 151 countries. One scenario describes the results of providing adults with ART as reported by countries between 1995 and 2009, the second scenario describes a situation in which no ART was provided to adults living with HIV between 1995 and 2009. The difference in the number of life-years accrued among adults in the two scenarios is compared and summarised by geographical region. RESULTS: An estimated 14.4 million life-years have been gained among adults globally between 1995 and 2009 as a result of ART. 54 % of these years were gained in western Europe and North America, where ART has been available for over 10 years. In recent years the growth in life-years has occurred more rapidly in sub-Saharan Africa and Asia. DISCUSSION: The substantial impact of ART described here provides evidence to argue for continued support of sustainable ART programmes in low and middle-income countries. Strengthening ART monitoring systems and mortality surveillance in low and middle-income countries will make this evidence more accessible to programme managers.

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.