Epidemiology of Tuberculosis in a High HIV Prevalence Population Provided with Enhanced Diagnosis of Symptomatic Disease
Elizabeth L. Corbett1,2*, Tsitsi Bandason2, Yin Bun Cheung1, Shungu Munyati3, Peter Godfrey-Faussett1, Richard Hayes1, Gavin Churchyard1, Anthony Butterworth12, Peter Mason2,4
1 London School of Hygiene and Tropical Medicine, London, United Kingdom, 2 Biomedical Research and Training Institute, Harare, Zimbabwe, 3 National Institute of Health Research, Harare, Zimbabwe, 4 Department of Medical Laboratory Sciences, University of Zimbabwe, Harare, Zimbabwe
Background
Directly observed treatment short course (DOTS), the global control strategy aimed at controlling tuberculosis (TB) transmission through prompt diagnosis of symptomatic smear-positive disease, has failed to prevent rising tuberculosis incidence rates in Africa brought about by the HIV epidemic. However, rising incidence does not necessarily imply failure to control tuberculosis transmission, which is primarily driven by prevalent infectious disease. We investigated the epidemiology of prevalent and incident TB in a high HIV prevalence population provided with enhanced primary health care.
Methods and Findings
Twenty-two businesses in Harare, Zimbabwe, were provided with free smear- and culture-based investigation of TB symptoms through occupational clinics. Anonymised HIV tests were requested from all employees. After 2 y of follow-up for incident TB, a culture-based survey for undiagnosed prevalent TB was conducted. A total of 6,440 of 7,478 eligible employees participated. HIV prevalence was 19%. For HIV-positive and -negative participants, the incidence of culture-positive tuberculosis was 25.3 and 1.3 per 1,000 person-years, respectively (adjusted incidence rate ratio = 18.8; 95% confidence interval [CI] = 10.3 to 34.5: population attributable fraction = 78%), and point prevalence after 2 y was 5.7 and 2.6 per 1,000 population (adjusted odds ratio = 1.7; 95% CI = 0.5 to 6.8: population attributable fraction = 14%). Most patients with prevalent culture-positive TB had subclinical disease when first detected.
Conclusions
Strategies based on prompt investigation of TB symptoms, such as DOTS, may be an effective way of controlling prevalent TB in high HIV prevalence populations. This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.
Funding: This study was funded by the Wellcome Trust. The funders had no role in the design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Academic Editor: Mario Raviglione, Stop TB-World Health Organization in Switzerland
Citation: Corbett EL, Bandason T, Cheung YB, Munyati S, Godfrey-Faussett P, et al. (2007) Epidemiology of Tuberculosis in a High HIV Prevalence Population Provided with Enhanced Diagnosis of Symptomatic Disease . PLoS Med 4(1): e22 doi:10.1371/journal.pmed.0040022
Received: May 10, 2006; Accepted: October 30, 2006; Published: January 2, 2007
Copyright: © 2007 Corbett et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abbreviations: CI, confidence interval; DOTS, directly observed treatment short course; IRR, incidence rate ratios; OR, odds ratio; PAF, population-attributable fraction; TB, tuberculosis; TST, tuberculin skin test; VCT, voluntary counselling and HIV testing; WHO, World Health Organization
* To whom correspondence should be addressed. E-mail: elc1@mweb.co.
