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Tuberculosis Infection in the United States

National Trends over Three Decades

¹ Centre for Research on Inner City Health, St. Michael's Hospital, Toronto, Ontario, Canada; ² Keenan Research Centre, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada; ³ Division of Infectious Diseases, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; ⁴ Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada; and ⁵ Division of Infectious Diseases, University Health Network, University of Toronto, Toronto, Ontario, Canada

Correspondence and requests for reprints should be addressed to Kamran Khan, M.D., M.P.H., St. Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8. E-mail: km.khan{at}utoronto.ca

Rationale: In 1989, the United States embarked upon an ambitious path to eliminate tuberculosis (TB) nationwide. Although incidence rates of TB disease in the United States are declining, these cases represent only a tiny fraction of all TB infections. Understanding national trends in TB infection may be important in anticipating future trends in TB disease.

Objectives: Describe the epidemiology of Mycobacterium tuberculosis infection in the United States in 1971–1972 and 1999–2000.

Methods: We studied nationally representative cohorts of the U.S. noninstitutionalized civilian population participating in the 1971–1972 and 1999–2000 National Health and Nutrition Examination Surveys. Participants were tuberculin skin tested and the epidemiology of TB infection was compared across surveys. Logistic regression was used to identify associations between participant and household characteristics and TB infection.

Measurements and Main Results: In 1999–2000, 4.2% (95% confidence interval [CI], 3.3–5.2%) of the U.S. population aged 1 year or older displayed evidence of TB infection. Among persons aged 25–74, the prevalence of infection decreased from 14.4% in 1971–1972 (95% CI, 11.6–17.7%) to 5.6% in 1999–2000 (95% CI, 4.4–7.1%). Declines in the relative burden of infection among persons aged 25–74 were greater in the United States–born population (12.6 to 2.5%) compared with the nation's foreign-born population (35.9 to 21.3%).

Conclusions: The United States has experienced a substantial decline in the burden of TB infection since the early 1970s. Despite this, the prevalence of infection among the nation's foreign-born population is over eight times greater than that observed in the United States–born population.

Key Words: tuberculosis • United States • public health • emigration and immigration • tuberculin test

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Most epidemiologic studies of tuberculosis infection in industrialized countries have been conducted on small populations at a single point in time and consequently have limited generalizability. What This Study Adds to the Field The United States has experienced a substantial decline in the burden of TB infection since the early 1970s. Despite this, the prevalence of infection among the nation's foreign-born population is over eight times greater than that observed in the United States–born population.

 

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