Use of tuberculosis genotyping for postoutbreak monitoring.

CONTEXT: Review of routinely collected tuberculosis genotyping results following a known outbreak is a potential mechanism to examine the effectiveness of outbreak control measures.
OBJECTIVE: To assess differences in characteristics between outbreak and postoutbreak tuberculosis cases.
DESIGN: Retrospective.
SETTING: United States. PARTICIPANTS: All tuberculosis cases identified as a result of >5-person outbreaks investigated by the Centers for Disease Control and Prevention during 2003 to 2007 (original outbreak cases), and subsequent culture-positive tuberculosis cases with matching Mycobacterium tuberculosis genotypes reported in the same county during 2004 to 2008 (postoutbreak cases). MAIN OUTCOME MEASURE: Proportion of demographic, social, and clinical characteristics of tuberculosis outbreak cases compared to postoutbreak cases. SECONDARY: Proportion of demographic, social, and clinical characteristics of epidemiologically linked versus nonlinked cases.
RESULTS: Six outbreaks with 111 outbreak cases and 110 postoutbreak cases were identified. Differences between outbreak and postoutbreak cases were gender (69% vs 85% male; P < .01), birth origin (3% vs 11% foreign-born; P = .02), disease severity (48% vs 62% sputum smear-positive; P = .04), homelessness (38% vs 51%; P = .05), and injection drug use (4% vs 11%; P = .04). For 5 of the 6 outbreaks, the status of epidemiologic relationships among postoutbreak cases was available (n = 89). The postoutbreak cases with a known epidemiologic link to the original outbreak were in younger persons (aged 39 vs 47 years; P < .01), and a larger proportion reported injection drug use (18% vs 4%; P = .04) or noninjection drug use (44% vs 18%; P < .01) than those without a reported link.
CONCLUSIONS: Health jurisdictions can utilize genotyping data to monitor and define the characteristics of postoutbreak cases related to the original outbreak.