Objective: To study the pattern of transmission of tuberculosis (TB) among foreign-born persons living in New York City.
Design: A retrospective multicenter study comparing 158 foreign-born patients to 231 US-born patients diagnosed with TB between 1992 and 1994. The patients were stratified according to their Mycobacterium tuberculosis isolate DNA fingerprint patterns.
Results: Nineteen (16%) of 122 isolates from foreign-born TB patients and 75 (42%) of 180 isolates from US-born TB patients had DNA fingerprint patterns (cluster patterns) indicative of recent exogenous transmission (P < 0.001). All cluster pattern strains from foreign-born cases were identical to those found among US-born patients. The likelihood of infection with a cluster pattern strain among foreign-born persons increased with duration of residence in the US, and was significantly associated with being homeless (P < 0.05), or having multidrug-resistant TB (P = 0.00072).
Conclusion: Although most (84%) cases of TB among foreign-born persons in New York City appear to result from reactivation of infections they acquired abroad, the ones who acquire new infections become infected with strains that are already circulating among the US-born TB patients in New York City, and they have risk factors similar to those faced by US-born tuberculosis patients.