Transmission of tuberculosis in San Francisco and its association with immigration and ethnicity

Martien W. Borgdorff, M. A. Behr, N. J.D. Nagelkerke, P. C. Hopewell, P. M. Small

Research output: Contribution to journalArticlepeer-review

90 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)287-294
Number of pages8
JournalInternational Journal of Tuberculosis and Lung Disease
Issue number4
Publication statusPublished - Apr 2000
Externally publishedYes


  • Molecular epidemiology
  • Reproductive rate
  • Transmission
  • Tuberculosis

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Infectious Diseases


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