Authors: M.W. Borgdorff¹; M.A. Behr²; N.J.D. Nagelkerke³; P.C. Hopewell⁴; P.M. Small²

Source: The International Journal of Tuberculosis and Lung Disease, Volume 4, Number 4, April 2000 , pp. 287-294(8)

Publisher: International Union Against Tuberculosis and Lung Disease

Abstract:

OBJECTIVE: To determine tuberculosis transmission dynamics in San Francisco and its association with country of birth and ethnicity.

METHODS: Restriction fragment length polymorphism (RFLP) typing was performed on Mycobacterium tuberculosis isolates from culture-positive pulmonary tuberculosis patients in San Francisco (1991 through 1996), using IS6110 as a probe. Patients were assigned to clusters based on mycobacterial isolates with identical DNA fingerprints. Clusters were assumed to have arisen from recent transmission. A transmission index was defined as the average number of culture-positive pulmonary tuberculosis cases generated by a single source case and calculated for subgroups.

RESULTS: The transmission index was higher in US-born (0.59) than in foreign-born groups (0.21), and was highest in blacks, in particular those aged under 35 years. The increased transmission index among blacks was not explained by smear-positivity, human immunodeficiency virus infection, or increased susceptibility to disease progression.

CONCLUSION: US-born tuberculosis cases generated more secondary cases than immigrants. Young blacks appear to be a high-risk group for tuberculosis transmission. These results suggest the need to develop interventions targeted towards this risk group.

Keywords: tuberculosis; transmission; molecular epidemiology; reproductive rate

Document Type: Regular paper

Affiliations: 1: Royal Netherlands Tuberculosis Association, The Hague, The Netherlands 2: Division of Infectious Diseases and Geographic Medicine, Stanford Medical Centre, Stanford, California, USA 3: Royal Netherlands Tuberculosis Association, The Hague, The Netherlands; and the Department of Public Health, Erasmus University Rotterdam, The Netherlands 4: Medical Service, San Francisco General Hospital, San Francisco, California, USA

Publication date: 2000-04-01

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• The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

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