In 1997, new cases of TB totaled an estimated 7.96 million (range, 6.3 million-11.1 million), including 3.52 million (2.8 million-4.9 million) cases (44%) of infectious pulmonary disease (smear-positive), and there were 16.2 million (12.1 million-22.5 million) existing cases of disease. An estimated 1.87 million (1.4 million-2.8 million) people died of TB and the global case fatality rate was 23% but exceeded 50% in some African countries with high HIV rates. Global prevalence of MTB infection was 32% (1.86 billion people). Eighty percent of all incident TB cases were found in 22 countries, with more than half the cases occurring in 5 Southeast Asian countries. Nine of 10 countries with the highest incidence rates per capita were in Africa. Prevalence of MTB/HIV coinfection worldwide was 0.18% and 640000 incident TB cases (8%) had HIV infection. The global burden of tuberculosis remains enormous, mainly because of poor control in Southeast Asia, sub-Saharan Africa, and eastern Europe, and because of high rates of M tuberculosis and HIV coinfection in some African countries.

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Short-course chemotherapy has substantially reduced TB mortality in half of China. The analytical method described here could be applied to TB control operations in many other countries, and should help to quantify the true burden of tuberculosis alleviated by SSCC.

ResultsCounties which had been enrolled in the programme since 1991 were, by 1997, preventing at least 46% (37-56%) of the TB deaths that would otherwise have occurred. If replicated across the entire TB control programme area, this would amount to 30 000 (range 26 000-59 000) deaths directly prevented each year.Conclusions Short-course chemotherapy has substantially reduced TB mortality in half of China. The analytical method described here could be applied to TB control operations in many other countries, and should help to quantify the true burden of tuberculosis alleviated by SSCC. KeywordsDisease burden, epidemiology, mathematical modelling, standard short-course chemotherapy, TB N)). This is a simple and easily measurable indicator which falls in value in a good control programme because, properly-treated, drug-susceptible cases infrequently require more than a single course of drugs. But it has the major weakness that it cannot be directly related to the change in illness and death. For example, a fall in prevalence will be reflected by a fall in T/N, but we expect both T and N to change as a result of intervention, so we cannot calculate the change in prevalence knowing only the ratio. The general problem is that we do not yet have a formal description of the properties of this potentially useful index, so its precise meaning remains unclear.Beginning with the notion that the re-treatment proportion provides a useful measure of the impact of TB control, our aim is to develop a more comprehensible method of measuring how effectively control programmes have reduced illness and deaths due to TB. The latter accounts for most of the burden in terms of years of healthy life lost. This paper concentrates on cases cured and deaths averted, using data from the first 7 years (1991)(1992)(1993)(1994)(1995)(1996)(1997) of the Chinese DOTS Programme. Methods A treatment-re-treatment model of tuberculosis controlThe outcome of treatment for patients in the Chinese Programme is well known: county data show treatment success (demonstrable smear conversion, or treatment completion) rates of over 90% and death rates of typically 2% or less. 3,4 However, these results refer only to patients observed in cohorts; we want to measure success with respect to the whole populations of counties and provinces enrolled in the Programme. Figure 1 depicts a simple model of the process of treatment and re-treatment for cases producing sputum smears that contain microscopically visible acid fast bacilli. New incident cases enter at the top of the diagram, and we assume that the rate at which they appear is constant through time. Most of these cases are presumed to seek treatment inside or outside the Programme, but some may die before being treated. A proportion of those who are treated will be cured (negative smear, or treatment completion), and the proportion depends on whether they are treated inside or outside the Programme. The rest fail, i.e. they have a persistently positive smear, they default (interrupt treatment), are transfe...

Objective To develop new methods for estimating the sputum smear-positive tuberculosis case detection rate (CDR) in a country where infection with HIV is prevalent. Methods We estimated the smear-positive tuberculosis CDR in HIV-negative and HIV-positive adults, and in all adults in Kenya. Data on time trends in tuberculosis case notification rates and on HIV infection prevalence in adults and in tuberculosis patients were used, along with data on tuberculosis control programme performance. Findings In 2006, the estimated smear-positive tuberculosis CDR in HIV-negative adults was 79% (95% confidence interval, CI: 64-94) and in HIV-positive adults, 57% (95% CI: 26-88), giving a weighted mean of 68% (95% CI: 49-87). The separate estimate for all smear-positive tuberculosis cases was 72% (95% CI: 53-91), giving an overall average for the three estimates of 70% (95% CI: 58-82). As the tuberculosis CDR in 1996 was 57% (95% CI: 47-67), the estimated increase by 2006 was 13 percentage points (95% CI: 6-20), or 23%. This increase was accompanied by a more than doubling of the resources devoted to tuberculosis control in Kenya, including facilities and staff. Conclusion Using three approaches to estimate the tuberculosis CDR in a country where HIV infection is prevalent, we showed that expansion of the tuberculosis control programme in Kenya led to an increase of 23% in the CDR between 1996 and 2006. While the methods developed here can be applied in other countries with a high prevalence of HIV infection, they rely on precise data on trends in such prevalence in the general population and among tuberculosis patients.Une traduction en français de ce résumé figure à la fin de l'article. Al final del artículo se facilita una traducción al español.