Prevalent infectious tuberculosis in Harare, Zimbabwe: burden, risk factors and implications for control
OBJECTIVES: To investigate the burden, duration and risk factors for prevalent tuberculosis (TB) and explore potential control strategies.
METHODS: Randomly selected adults had TB culture, symptom screen and human immunodeficiency virus (HIV) serology. Prevalent TB was defined as undiagnosed or still culture-positive. Notification data and HIV prevalence in TB out-patients were used to estimate duration of infectiousness (prevalence/estimated incidence).
RESULTS: Among 10 092 participants, 40 (0.40%, 95%CI 0.28–0.54) had prevalent smear-positive TB. HIV (adjusted odds ratio [aOR] 3.1, 95%CI 1.6–6.3, population attributable fraction [PAF] 33%), male sex (aOR 3.1, 95%CI 1.5–6.4, PAF 40%), and overcrowding (PAF 34%) were significant risk factors, with past TB treatment significant for HIV-negative participants only (PAF 7%). Recent household TB contact was not significant (PAF 10%). HIV prevalence was 21.1%; 76.9% of HIV-positive participants were previously untested. Duration of infectiousness was at least 18 weeks in HIV-positive and approximately 1 year in HIV-negative patients.
CONCLUSIONS: Overcrowding, male sex and HIV infection were major risk factors for prevalent smear-positive TB. Reducing diagnostic delay may have greater potential to improve the control of prevalent TB than interventions targeted at household contacts, TB treatment outcomes, or TB-HIV interventions under current levels of awareness of HIV status.
Document Type: Regular Paper
Affiliations: 1: Clinical Research Unit, London School of Hygiene & Tropical Medicine (LSHTM), London, UK; Biomedical Research and Training Institute, Harare, Zimbabwe 2: Biomedical Research and Training Institute, Harare, Zimbabwe 3: Infectious Disease Epidemiology Unit, LSHTM, London, UK 4: Biomedical Research and Training Institute, Harare, Zimbabwe; and National Institute of Health Research, Harare, Zimbabwe 5: Aurum Institute, Johannesburg, South Africa 6: Stop TB Department, World Health Organization, Geneva, Switzerland 7: Clinical Research Unit, London School of Hygiene & Tropical Medicine (LSHTM), London, UK; and Biomedical Research and Training Institute, Harare, Zimbabwe 8: Harare City Health, Harare, Zimbabwe 9: Biomedical Research and Training Institute, Harare, Zimbabwe; and University of Zimbabwe Medical School, Harare, Zimbabwe
Publication date: 2009-10-01
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