A baseline CD4+ T-lymphocyte count <200 cells/mm3 [HR 2.5; (95% CI 1.2, 5.4); p<0.01], prior hospitalization [HR 4.2; (95% CI 2.0, 8.8); p<0.001] , prior incarceration [HR 4.1; 95% CI 1.6, 10.3); p<0.01], and a positive tuberculin skin test [HR 3.1; (95% 1.1, 9.0); p = 0.04] were independently and positively associated with incident TB. The gene discussed is CD4; the disease is tuberculosis.