Tuberculosis

Tuberculosis is the leading infectious cause of death worldwide, being responsible for 3 million deaths annually. Among those aged over 5 years, tuberculosis kills more people than AIDS, malaria, diarrhoea, leprosy, and all other tropical diseases combined. The tragedy of this situation is that treating tuberculosis is one of the most effective and cost effective of all health interventions. The World Health Organisation has calculated that, unless urgent action is taken, the annual number of deaths could rise from 3 million to 4 million by the year 2004.1 We urgently need improvements in the implementation of existing strategies for tuberculosis control, with particular emphasis on early diagnosis and delivery of effective treatments. In addition, basic research is needed for the development of simple and rapid diagnostic tests, more effective vaccines, and new drugs. This article focuses on new scientific approaches to tuberculosis control that could soon be incorporated into routine practice. However, the impact of new approaches will be negligible if the wealthy Western nations fail to address the gross global inequities in healthcare provision,2 which account for the fact that 98% of deaths from tuberculosis occur in the poorer developing countries (fig ​(fig1).1). Figure 1 Estimated incidence and prevalence of, and number of deaths due to, tuberculosis in 1997 (data from World Health Organisation3) So serious is the global threat of tuberculosis that, in 1993, the WHO took the unprecedented step of declaring this disease a global emergency.1 The problem is fuelled by the pandemic of HIV infection and AIDS and the emergence of drug and multidrug resistance. HIV infection renders a person infected by Mycobacterium tuberculosis much more likely to develop overt tuberculosis, and the evolution of the disease is considerably accelerated. At present, about 8-10% of all cases of tuberculosis worldwide are related to HIV infection, but the association is much more common in many African countries, often 20% or more.4 Drug resistance is ubiquitous, although the incidence varies greatly from region to region. Globally, about 10% of cases of tuberculosis are resistant to one drug, and, although primary multidrug resistance is uncommon (about 0.2%), it occurs in a median of 4.4% of previously treated patients.5 These figures may be an underestimate, as countries with good facilities for testing for drug resistance also have good tuberculosis control programmes. Potential futures Nucleic acid technology will provide rapid, specific, and sensitive diagnostic tests and rapid detection of drug resistance A new vaccine able to prevent the emergence of post-primary, infectious tuberculosis will be one of the principal means of controlling tuberculosis An immunotherapeutic agent used in conjunction with drug treatment will lead to a much lower failure rate, even in cases of drug resistant disease, and new “designer” drugs with specific anti-tuberculosis activity will be used to treat resistant cases Anti-HIV vaccines will reduce the burden of HIV related tuberculosis Adequate resources to implement the directly observed therapy short course (DOTS) strategy will be made available to developing countries by the Western nations The social factors responsible for the global emergency of tuberculosis—poverty, injustice, and conflict—will be more seriously considered and addressed