Karen Stanecki

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.

Improved methods and assumptions for estimation of the HIV/AIDS epidemic and its impact: Recommendations of the UNAIDS Reference Group on estimates, modelling and projections

UNAIDS and WHO produce biannual country-specific estimates of HIV/AIDS and its impact. These estimates are based on methods and assumptions that reflect the best understanding of HIV epidemiology and demography at the time. Where significant advances are made in epidemiological and demographic research, the methods and assumptions must evolve to match these advances. UNAIDS established an Epidemiology Reference Group in 1999 to advise them and other organisations on HIV epidemiology and methods for making estimates and projections of HIV/AIDS. During the meeting of the reference group in 2001, four priority areas were identified where methods and assumptions should be reviewed and perhaps modified: a) models of the HIV epidemic, b) survival of adults with HIV-1 in low and middle income countries, c) survival of children with HIV-1 in low and middle income countries, and d) methods to estimate numbers of AIDS orphans. Research and literature reviews were carried out by Reference Group members and invited specialists, prior to meetings held during 2001-2. Recommendations reflecting the consensus of the meeting participants on the four priority areas were determined at each meeting. These recommendations were followed in UNAIDS and WHO development of country-specific estimates of HIV/AIDS and its impact for end of 2001.UNAIDS and WHO produce biannual country-specific estimates of HIV/AIDS and its impact. These estimates are based on methods and assumptions that reflect the best understanding of HIV epidemiology and demography at the time. Where significant advances are made in epidemiological and demographic research, the methods and assumptions must evolve to match these advances. UNAIDS established an Epidemiology Reference Group in 1999 to advise them and other organisations on HIV epidemiology and methods for making estimates and projections of HIV/AIDS. During the meeting of the reference group in 2001, four priority areas were identified where methods and assumptions should be reviewed and perhaps modified: a) models of the HIV epidemic, b) survival of adults with HIV-1 in low and middle income countries, c) survival of children with HIV-1 in low and middle income countries, and d) methods to estimate numbers of AIDS orphans. Research and literature reviews were carried out by Reference Group members and invited specialists, prior to meetings held during 2001-2. Recommendations reflecting the consensus of the meeting participants on the four priority areas were determined at each meeting. These recommendations were followed in UNAIDS and WHO development of country-specific estimates of HIV/AIDS and its impact for end of 2001.

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 12u2005months (with ARV prophylaxis) could avert an additional 264u2008000 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.

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.

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 700u2008000 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 10u2005years. 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.

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 <5u2005years. 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.

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

ABSTRACT 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.

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 710u2008000 (610u2008000–780u2008000) to 950u2008000 (810u2008000–1.0 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.

How bad will it be? Modelling the AIDS epidemic in Eastern Africa

The spread of HIV infection and the subsequent AIDS morbidity and mortality threatens to have a substantial impact on societies in subSaharan Africa. Infection levels are increasing rapidly in many regions, especially in urban areas. The consequences of high levels of infection are inescapable, although, due to the long incubation period, morbidity and mortality increases lag several years behind increases in infection levels. The impact of a serious AIDS epidemic will be felt by many sectors of the society. Mortality levels will substantially increase, especially among newborns and adults under age 50. This mortality will remove many productive members from the economy, while HIV-related illness will reduce the productivity of the infected population. Health care facilities will be severely strained to bear the increases in hospitalized populations. Those without access to the formal health care system will rely on family members for support and care.