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This chapter is from the book

This chapter is from the book

Scenarios for the pandemic's future

Perhaps the clearest message of the pandemic's history to date is that concerted action can make a difference. Antiretroviral treatment had saved 2.9 million lives worldwide between 1996 and 2008.50 Similarly, as Figure 1.11 shows, expanded access to services to prevent mother-to-child HIV transmission averted at least 200,000 new infections globally between 1996 and 2008, with these life-saving results increasing from year to year as services have been expanded.51

Figure 1.11

Figure 1.11 Estimate of the annual number of infant infections averted through the provision of antiretroviral prophylaxis to HIV-positive pregnant women globally (1996–2008).

Source: WHO/UNAIDS 2009 AIDS epidemic update.

The magnitude and quality of the continued response to AIDS will be determining factors in the pandemic's future. To clarify the long-term implications of choices to be made in the coming years, the aids2031 Modeling Working Group produced a series of mathematical models on potential AIDS futures in 22 countries, including 12 in Africa (Cameroon, Ethiopia, Kenya, Malawi, Mozambique, Nigeria, South Africa, Sudan, Tanzania, Uganda, Zimbabwe, and Zambia), six in Asia (Cambodia, China, India, Indonesia, Thailand, and Vietnam), two in Eastern Europe (Russia and Ukraine), and two in Latin America (Brazil and Mexico). For each of these countries, the model took into account the interaction between different sexually transmitted diseases and HIV, the role of heterogeneity in sexual behavior, patterns of sexual acts within partnerships, networks of concurrent sexual partnerships, patterns of incidence as a function of age, and the impact of interventions. For intervention impact, the modelers relied on the public health literature, including clinical trials and epidemiological studies; the models all assumed constant coverage and impact from 2015 onward. Models further assumed that receipt of antiretroviral therapy would reduce the likelihood of onward HIV transmission, a conclusion that is consistent with numerous studies that have correlated viral load with transmissibility.

Using these various data sources, modelers charted the likely future of epidemics in these 22 countries according to various scenarios, calculating the number of incident infections, total HIV prevalence in 2031, and the number of AIDS deaths likely to occur under each scenario between 2010 and 2031. Importantly, the models aim to quantify the long-term impact of choices that will be made in the next several years, tracing the ultimate impact in 2031 to political choices made between 2010 and 2015. One possible future scenario, the "status quo" scenario, calculates results based on a continuation of current coverage levels. A second scenario envisages an intensification of HIV prevention and treatment programs toward saturation coverage.

The results of the modeling exercises led to several fundamental conclusions about the epidemic's future and the choices facing global decision-makers over the course of the next several years.

Choices made in the next five years will profoundly affect how the pandemic will look in 2031

Maintaining existing coverage levels would allow nearly 50 million cumulative new infections among 15- to 49-year-olds in these 22 countries by 2031. By contrast, as shown in Figure 1.12, expanded coverage would avert more than 26 million of these infections (or more than half).

Figure 1.12

Figure 1.12 Projection of new HIV infections and number of adults infected according to status quo and an expanded scenario based on information received from 22 countries.

Source: aids2031 Modeling Working Group (unpublished data)

The impact of these choices in specific countries is revealing. Consider South Africa, for example, home to the world's largest number of people living with HIV. If current coverage levels continued, HIV prevalence in 2031 would be the same (18%) as it was in 2008, the most recent year for which data is available.52 Yet this stability in prevalence is deceiving; with the projected growth in population, a stable prevalence would mean 12 million new infections between now and 2031. By contrast, if AIDS response efforts are strengthened over the next several years, HIV prevalence would be one-third lower in 2031, assuming that scaled-up treatment will help slow the rate of new infections by lowering the level of virus circulating in communities. In Nigeria, Mozambique, and Zambia, reductions would be even sharper, with projected prevalence in 2031 nearly 50% lower under an intensified response. The flattening of all the curves after 2015 reflects the assumption that all intervention coverage and impacts is constant after that date.

In Zambia, the annual number of new infections in 2031 would be nearly four times greater with a continuation of current service coverage than with an intensified, expanded response, as Figure 1.13 shows. In China, where population growth will be a critical driver in the number of new HIV infections over the next generation, the status quo scenario would result in more than three times as many incident infections in 2031 as in an expanded response, also shown in Figure 1.13. HIV-related deaths in Zambia would be more than twice as high in 2031 if current coverage levels continue, and the mortality rate in China would be more than three times as high.

Figure 1.13

Figure 1.13 Current and projected annual new HIV infections in adults (15–49 years) in China and Zambia, according to different scenarios.

Source: WHO/UNAIDS 2009 AIDS epidemic update.

To achieve dramatic change, all available tools must be used to their maximum advantage

To avert tens of millions of deaths over the next generation, as projected in the most favorable scenario, the best results possible must be obtained with the available tools. This demands continuous quality improvement, results-based management, and program evaluation to improve performance over time (see Chapter 3, "Using knowledge for a better future"). Such improvements over time could be expected to continue beyond 2015, leading to better future results than shown in the projections.

Prioritizing HIV prevention is critical to accelerated progress between now and 2031

The level of resources devoted to HIV treatment in low- and middle-income countries is roughly 2.5 times greater than amounts dedicated to HIV prevention.53 Increasingly, AIDS efforts are characterized by an approach that focuses almost exclusively on treating existing infections and devotes meager resources to preventing new infections. This approach mimics the path high-income countries have taken. In the United States, for example, only 3% of government outlays for HIV are currently allocated to prevention programs.54 Without substantial targeted HIV prevention efforts, new HIV infections will continue to outpace treatment efforts—even while recognizing some prevention efforts from expanded treatment.

Figure 1.14 demonstrates that the long-term results of this approach would be potentially devastating in resource-limited settings. In Zambia, nearly twice as many incident infections would occur in 2031 under a treatment-only approach as would occur with a combination of robust prevention and treatment efforts.

Figure 1.14

Figure 1.14 Current and projected impact of intervention strategies on new HIV infections among adults in Zambia.

Source: aids2031 unpublished data.

To achieve optimal results for 2031, new prevention tools will be needed

To make truly revolutionary gains in the epidemic over the next two decades, new and better prevention tools are needed, along with structural changes in many communities and societies. According to the aids2031 Modeling Working Group, achieving a 90% reduction in HIV incidence by 2031 necessitates a 70% reduction in the average number of sexual partners.55 This effect far exceeds results obtained with existing prevention tools, pointing to the need for additional prevention options and a broader approach to prevention that accounts for social drivers of national epidemics.

Figure 1.12 is telling. With an expanded response that achieves maximum coverage for both HIV prevention and treatment, the annual number of new HIV infections in Zambia would be half what it was in 2001 and roughly 50% lower than current HIV incidence. This would represent significant progress, but it would still leave Zambia grappling with an enormous health crisis that would sap national resources and push countless households into poverty.

The world should aim higher. However, reaching this lofty goal will require new scientific tools and improved knowledge about ways to change sexual behavior and prevent new infections, topics that the following chapter addresses in depth.

Delivering treatment to those who need it will be vital to minimizing the pandemic's impact

Securing the gains envisaged in the intensified/expanded scenario will require continued, sustained support for scaling up HIV treatment. As Figure 1.15 illustrates, current coverage trends would cover fewer than half the number of people who would receive treatment under the optimal scenario in 2016. By 2031, the number of people receiving treatment in the optimal scenario would be more than 60% higher than with current trends.

Figure 1.15

Figure 1.15 Current and projected number of adults (15–49 years) receiving treatment in Zambia.

Source: aids2031 unpublished data.

These projections underscore the need to intensify measures to mitigate the pandemic's impact

An important lesson learned thus far in the global AIDS response is that even the most heavily affected societies have proven to be far more resilient than projected earlier in the epidemic.56 Yet this resilience masks enormous individual and societal burdens, many of which are likely to endure for generations.

A case in point is the extraordinary number of the world's children who have been orphaned by the pandemic. In sub-Saharan Africa, more than 14.8 million children have lost one or both parents to AIDS.57 As the projections summarize, vulnerable households will still face significant numbers of deaths and further burdens, even under the most favorable scenarios.58

Over the last three decades, the primary focus of the AIDS response has been on getting programs up and running, frequently in communities with little health infrastructure. In many cases, the goal has been to achieve immediate results. In some cases, responses have been premised on the expectation that an imminent biomedical breakthrough will resolve the need for further action. Typically, more difficult challenges—such as changing community norms or gender relations, or addressing the impact of labor or economic structures on individual or collective vulnerability—have been dismissed as too long range and time-intensive to merit investment in the context of an emergency.

The overarching theme of this report is that AIDS is a generations-long challenge and thus requires a generations-long response that adopts a longer-term mindset. In moving forward, the imperative of scaling up must be matched by an equally strong commitment to quality, efficiency, and sustainability. And, to achieve long-term success with AIDS, underlying drivers of national and local epidemics must be addressed, even if these efforts are unlikely to achieve results in the short term. Table 1.1 details the characteristics of the long-term and short-term approaches.

Table 1.1. Selected characteristics of shifting from a short-term to long-term approach

Short Term

Long Term



Generic approach

Locally adapted approaches

Donor-imposed short-term (1–2 year) funding

Locally designed multiyear plans and financing (5–15 years)

External consultants

Investment in local capacity

AIDS isolated from broader health and development

Synergies with other health and development

Individual behavior change

Societal and individual behavior change

As with any effort that must be sustained over many years, complacency and denial are the enemies of long-term success; already, signs of the world's fading interest in AIDS are apparent. But with concerted efforts and a changed approach as described in this book, success in the AIDS response is achievable. A great deal of the knowledge needed to radically reduce the number of new HIV infections and AIDS deaths over the next generation is already available, and the world possesses the research capacity to generate the new preventive and therapeutic tools that will be required. Even in the midst of worldwide economic uncertainty and anxiety, little doubt arises that sufficient resources exist to address AIDS and other global health challenges.

The subsequent chapters detail the steps needed to place a global AIDS response on a long-term and sustainable footing. In the final chapter, the aids2031 Consortium offers recommendations for the steps that need to be taken now to ensure long-range success.

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