Background

Tuberculosis has long been the scourge of humanity, claiming millions of lives. Evidence of its antiquity is available in the form of Egyptian and South American mummies, dating from 3000–5000 years BC, with symptoms typical of Potts disease, a rare tuberculous manifestation affecting the spine (Haas & Haas, 1996; Salo et al., 1994). In Europe, pulmonary tuberculosis was the major cause of death in the 18–19th centuries, and during the industrial revolution its spread was facilitated by poor housing, bad sanitation, overcrowding and malnutrition. As living conditions improved, tuberculosis receded in the Western world but assumed greater prevalence in many developing countries where it had previously been of lesser importance. In part, this was due to demographic factors like those encountered during the industrial revolution, such as displacement of populations and urbanization. More recently, the HIV\AIDS epidemic has greatly exacerbated an already grave situation in the developing world by creating a deadly synergy with tuberculosis that leads to even worse morbidity and mortality (Murray, 1990).

At the present time, the World Health Organization estimates that eight million new cases of tuberculosis occur every year and that 25 million individuals worldwide will lose their lives to the disease in the coming decade (Dye et al., 1999). Although the ultimate solution to the problem of tuberculosis will be socio-economic, many of these deaths could be prevented if better access to treatment were available and if vaccination were more effective. More alarmingly, on the basis of their tuberculin reactivity, a sign of prior infection, it has been calculated that one-third of the world’s population has been infected with Mycobacterium tuberculosis (Dye et al., 1999), the aetiological agent of the disease. These