Global epidemiology of tuberculosis

Tuberculosis is the leading cause of death from a curable infectious disease.1 On the basis of results of surveys of the prevalence of infection and disease, assessments of the effectiveness of surveillance systems, and death registrations, there were an estimated 8.9 million new cases of tuberculosis in 2004, fewer than half of which were reported to public-health authorities and WHO. In African populations with high rates of HIV infection, a relatively high proportion of patients with tuberculosis are women aged 15-24 years.3,4 The rise in the number of tuberculosis cases is slowing in Africa, almost certainly because HIV infection rates are beginning to stabilise or fall.9 HIV has probably had a smaller effect on tuberculosis prevalence than on incidence because the virus significantly reduces the life expectancy of patients with tuberculosis.10 Where HIV infection rates are high in the general population they are also high among patients with tuberculosis; estimates for 2004 exceeded 50% in Botswana, South Africa, Zambia, and Zimbabwe, among other countries.