title: Tuberculosis infection in the United States: national trends over three decades.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  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.
  
  
  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.
authors.affiliation: St. Michael's Hospital, 30 Bond Street, Toronto, ON, Canada. km.khan@utoronto.ca
authors.forename: Kamran
authors.initials: K
authors.lastname: Khan
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.forename: Arlene
authors.initials: A
authors.lastname: Bierman
authors.forename: Yukit
authors.initials: Y
authors.lastname: Li
authors.forename: Michael
authors.initials: M
authors.lastname: Gardam
mesh_terms: D017677:Age Distribution; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006306:Health Surveys; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D015995:Prevalence; D011336:Probability; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D015996:Survival Rate; D013997:Time Factors; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology