Tuberculosis deaths in countries with high HIV prevalence: what is their use as an indicator in tuberculosis programme monitoring and epidemiological surveillance?

Although the reduction of tuberculosis deaths is one of the aims of tuberculosis control, it has not always been a priority for National Tuberculosis Programmes (NTPs). The usual explanation is that death as a treatment outcome not associated with ongoing tuberculosis transmission is not relevant to the public health objective of cutting the cycle of disease transmission. However, death as an adverse outcome for tuberculosis patients and their families is an important indicator in NTP monitoring. Global health targets agreed as part of the Millennium Development Goals include the reduction of tuberculosis deaths. Tuberculosis deaths as an indicator of the impact of tuberculosis control measures are therefore important in the epidemiological surveillance of progress towards these targets. These considerations are particularly important in countries with high human immunodeficiency virus (HIV) prevalence where HIV has exacerbated the tuberculosis epidemic and is now the single best predictor of tuberculosis incidence. Tuberculosis deaths are also closely linked to HIV prevalence. Routine NTP data on tuberculosis cohort deaths are important in programme monitoring, and improvements in recording and reporting of deaths would help to overcome limitations in their accuracy. As routine NTP data on tuberculosis cohort deaths are insufficient as an indicator in epidemiological surveillance regarding the impact of NTPs on tuberculosis mortality, measuring progress towards targets for reduced tuberculosis deaths depends on improved national vital registration systems for a more accurate determination of tuberculosis mortality.

The dynamics of tuberculosis in response to 10 years of intensive control effort in Peru.

Improved tuberculosis (TB) case detection and cure rates are expected to accelerate the decline in incidence of TB and to reduce TB-associated deaths. Time series analyses of case reports in Peru showed that the per capita TB incidence rate was probably steady before 1991. Case reports increased between 1990 and 1992 as a result of improved case detection. Although diagnostic efforts have continued to increase since 1993, the incidence of new pulmonary TB cases has declined in every department of the country, with a national rate of decline > or =5.8% per year (range, 1.9%-9.7%). This elevated rate of decline suggests that 27% (19%-34%) of cases (158,000) and 70% (63%-77%) of deaths (91,000) among smear-positive patients were averted between 1991 and 2000. This is the first demonstration that a significant number of TB cases can be prevented through intensive short-course chemotherapy in a high-burden country.

The epidemiology of BSE in cattle herds in Great Britain. I. Epidemiological processes, demography of cattle and approaches to control by culling.

This paper explores the key epidemiological processes and demographic factors that determined the pattern of transmission of the aetiological agent of bovine spongiform encephalopathy (BSE) in cattle herds in Great Britain (GB). The analyses presented utilize data from published and unpublished experimental studies and from the GB central database of confirmed BSE cases. We review the experimental and epidemiological evidence that has both confirmed indirect horizontal transmission via the consumption of infectious material as the major transmission route and provided information on the duration and variability of the dose-dependent incubation period of BSE in cattle. The epidemiological and genetic data pertaining to the possible existence of maternal transmission and/or genetically variable susceptibility to infection is discussed. The demography of British cattle is characterized and the impacts of key demographic features on the observed epidemic profile are discussed. In the main BSE case database, analyses reveal that BSE cases cluster significantly at both the holding and county scale. Furthermore, analysis of longitudinal patterns reveal substantial temporal within-holding correlation. Such clustering of cases suggests a highly heterogeneous infection process. The paper ends with a discussion of how analyses of spatio-temporal clustering inform the design of targeted culling programmes aimed at reducing future disease incidence. We show how the retrospective implementation of culling policies on the BSE case database allows the qualitative evaluation of policy performance, but that model predictions of future trends in case incidence are required to estimate the precise impact of any current or future programme.

Transmission dynamics and epidemiology of BSE in British cattle.

A comprehensive analysis of the bovine spongiform encephalopathy (BSE) epidemic in cattle in Great Britain assesses past, present and future patterns in the incidence of infection and disease, and allows a critical appraisal of different culling policies for eradication of the disease.