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Incidence rate of secondary cases, index cases/unique cases, and unknown (not determined) genotyping cases of tuberculosis among foreign-born patients in San Francisco from 1991 through 2009 (n = 2,419), assessed using a 1-year window period (foreign-born secondary cases decreasing: P < 0.001; coefficient, –0.12; foreign-born index/unique cases decreasing: P < 0.001; coefficient, –0.05).
