Tuberculosis: 12. Global disease and the role of international collaboration.

T he burden of tuberculosis (TB) today is greatest in low-income countries: over 90% of all cases arise there, and over 95% of deaths from the disease occur there; 1 moreover, a high and increasing proportion of cases in many industrialized countries occur in people who were born and became infected in low-income countries, before they moved to the country where their TB has been detected. 2 The horrendous impact of the HIV epidemic, including its pathophysiologi-cal, clinical and epidemiological interaction with TB, 3 has been most evident in sub-Saharan Africa (particularly eastern and southern Africa) and is rapidly becoming apparent in India and Thailand. Estimates of the global impact of TB indicate that TB is the most frequent cause of death in the world from a single agent in young adults 1 and that at least 20 million people have died unnecessarily of this disease in the past decade. These facts necessitate international collaboration in interventions to deal with TB. In this paper I present an overview of global interventions to eliminate TB, focusing in particular on the roles of scientific and technical experts , government agencies, and voluntary associations in these cooperative efforts. To be effective, global action on TB must have clear objectives. Ultimately, the aim of any interventions should be elimination of the disease. Global elimination of an infectious disease has been achieved only once before, for smallpox, but there are divergent views as to whether this goal can be accomplished for TB. The following characteristics facilitated the elimination of smallpox: an effective vaccination strategy, no natural reservoir outside humans and no carrier state for the virus. TB does not have these characteristics. Instead, the prevention strategy is based on case management, there are animal reservoirs of the bacteria and most infected people carry viable bacilli without symptoms. On what grounds, then, can we hope that TB can be eliminated? A vaccine containing attenuated Mycobacterium bovis, developed by Calmette and Guérin 4 (the bacille Calmette–Guérin [BCG] vaccine) was tested in humans in 1921, and the results were promising. 5 After World War II, rigorous efficacy trials were undertaken, 6 a comprehensive program for administration of the vaccine was developed 7 and an extensive program of epidemiological research into the prevalence of TB disease and infection was launched. Although the protective efficacy of BCG vaccination was demonstrated in many trials, its role in preventing TB infection was …