Intro
Despite the availability of drugs to cure tuberculosis (TB) since the 1940s, TB remains an important cause of death from an infectious agent, second only to the human immunodeficiency virus, or HIV (WHO 2004f). TB control is high on the international public health agenda, not only because of the enormous burden of disease, but also because short-course chemotherapy (SCC) is recognized as one of the most cost-effective of all health interventions (Jamison and others 1993). That recognition is partly attributable to an influential series of studies done in three of the poorest countries of southeastern Africa (Malawi, Mozambique, and Tanzania), which suggested that a year of healthy life could be gained for less than about US$5 (de Jonghe and others 1994; Murray and others 1991). This evidence has been central to the global promotion of the DOTS strategy, the package of measures combining best practices in the diagnosis and treatment of patients with active TB, in which direct observation of treatment during SCC is a key element (WHO 2002a, 2004c).
Although the World Health Organization (WHO) has fostered the implementation of DOTS over the past decade, four recent developments have drawn attention to a wider range of options for TB control:
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First, many more studies have investigated the costs, efficacy, and cost-effectiveness of different approaches to TB control. They are mostly studies of ways to improve the delivery of first-line drug treatment for active disease, but they include some investigations of preventive therapy (treatment of latent infection), treatment of multidrug-resistant TB (MDR-TB) using both first- and second-line drugs, and different approaches to diagnosis. They have been carried out in a variety of settings, in richer as well as poorer countries. The results have not been fully synthesized but may suggest ways to enhance DOTS.
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Second, striking increases in TB have been associated with the spread of HIV infection and drug resistance, suggesting that DOTS alone may not be enough to bring TB under control, especially in Africa and in the countries of the former Soviet Union.
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Third, there is now substantially more investment in new tools for TB control, including multimillion-dollar initiatives to develop better diagnostics, drugs, and vaccines, many of which operate under the umbrella of the Stop TB Partnership (see http://www.stoptb.org). Some of the possible products of this new research would stimulate reevaluations of the current reliance on chemotherapy, especially the development of a new high-efficacy vaccine.
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Fourth, interest in TB is renascent, not simply as the outcome of mycobacterial infection, but also as the consequence of exposure to exacerbating risks, such as tobacco smoke, air pollution, malnutrition, overcrowding, and poor access to health services. Research directed at quantifying these risks will also suggest ways to minimize them.
These developments set a big agenda for analysis. To make some inroads, this chapter presents an overview of the value for money and potential effect of the principal modes of TB control around the world. The starting point is a review of the natural history and clinical characteristics of TB and the geographical distribution of and trends in TB cases and deaths. This introduction sets the context for a discussion of the interventions that are now available to control TB and of how they have been used. We use a new method for evaluating the cost-effectiveness of infectious disease control and apply this method systematically to four groups of TB interventions as they could be implemented in six regions of the world.
The internationally agreed-on targets for TB control, embraced by the United Nations Millennium Development Goals (MDGs), are to detect 70 percent of sputum-smear-positive cases and successfully treat 85 percent of such cases by the end of 2005. The expectation is that, if these targets can be reached and maintained, incidence rates will be falling by 2015, and the TB prevalence and death rates of 1990 will be halved by 2015. Meeting these targets requires a set of interventions that are not only cost-effective but also affordable and capable of having an effect on a large scale. The final sections of the chapter discuss the absolute costs and benefits of global TB control and the potential for achieving the effect defined within the MDG framework. The main themes of the text that follows are elaborated in a series of annexes available online at http://www.fic.nih.gov/dcpp as well as at http://www.who.int/tb/publications/en/.
