© 2006 American Thoracic Society doi: 10.1164/rccm.200606-756ED
Universal Genotyping as a Tool for Establishing Successful Partnerships for Tuberculosis EliminationDenver Public Health, Denver, Colorado In this issue of the Journal (pp. 599–604), Moonan and colleagues describe the initial outcomes of a tuberculosis control intervention in Tarrant County, Texas, involving three small communities that have registered exceedingly high rates of tuberculosis for nearly a decade (1). The tuberculosis risk factors within these zip code–defined communities include high rates of unemployment, homelessness, and substance abuse. Previous reports from the Tarrant County Public Health Department indicate that these focal communities have been impacted by recurrent and/or persistent high rates of tuberculosis transmission despite previous intervention efforts (2, 3). The importance of this new report lies in understanding how local public health officials, using information from universal Mycobacterium tuberculosis strain genotyping and Geographic Information System (GIS) analysis, were able to develop and initiate a highly successful tuberculosis control intervention. It is important that we understand the nature of the tuberculosis problem to gain insights into why previous intervention efforts were not successful, as well as why this new and promising approach may be successful. Based on previous studies, it appears certain that several congregate living settings serving the homeless have inadvertently served as sites of intermittent and/or ongoing transmission within the three high-risk zip codes selected for intervention (2, 4). An analysis of tuberculosis cases diagnosed during 1996–1997 in Tarrant County found clustering of tuberculosis case isolates to be strongly associated with a history of homelessness, but not HIV infection; isolates from 83% of 35 cases among homeless persons were clustered (4). The 2004 publication of the GIS analysis of genotypic and epidemiologic data spanning the 8-year period 1993–2000 documented average annual tuberculosis incidence rates of 94, 55, and 32 cases per 100,000 populations in the three high-risk zip codes. Genotypic clustering was observed in 95 (81%) of 117 case isolates over this 8-year period. The association with residence in homeless shelters was again illustrated with the GIS analysis. Clustering was found in 29 case isolates from residents of Shelter A in Zip Code 1, accounting for 71% of the 41 clustered isolates in that zip code over the 8-year period (2). Given the evidence supporting homeless shelters as transmission locations, why was the previous shelter screening not successful? Shelter residents have been offered tuberculosis screening, testing, and treatment for latent tuberculosis infection since 1991. The evidence indicates the procedure used was low-yield in terms of case finding, detecting only 5% of active tuberculosis cases occurring among shelter residents (the remainder being diagnosed in area hospitals) (3). In contrast, the location-based program described in the present report detected 20 cases of active tuberculosis among the first 702 individuals screened by chest radiography in September 2002. The 2.9% active tuberculosis prevalence rate at the first screening and the prevalence of 1.9% during the entire first year are exceeded in United States' residents only by case-finding rates reported during tuberculosis outbreaks in homeless shelters, and rival rates found during evaluation of contacts of infectious tuberculosis cases (5). The advantages of expanding the tuberculosis screening sites from homeless shelters to other "location-based" community organizations serving the population at risk likely include better access for the population, as well as the opportunity to screen those who may have been previously exposed in shelters but were no longer shelter residents. In the 1996–1997 Fort Worth study, only 11 of the 35 individuals with tuberculosis and a history of homelessness were shelter residents at the time of diagnosis (4). However, a major difference was the transition from providing voluntary screening to requiring tuberculosis screening at yearly intervals. This mandatory screening requirement was apparently not accomplished by health department regulation but rather was an administrative decision made by most of the community-based organizations. After being presented with the epidemiologic data, these organizations partnered with the local public health department by making annual tuberculosis screening a condition for continuing to receive a variety of services, including emergency housing (1). The major contribution of this article is not how molecular epidemiology and geographical analysis enabled the epidemiologist to define the problem, but how these data were used as a tool in garnering the critical support of community-based organizations. The short-term findings are encouraging; the prevalence of active tuberculosis dropped from 1.9% during the first 12 months of screening to 0.5% during screening done during the last 16 months. Although beyond the scope of this initial report, the long-term effect of this partnership and intervention will be important to measure, including outcomes of treatment for active tuberculosis and latent tuberculosis infection. In addition to follow-up on the outcome of this intervention, an analysis of the services received by the screened individuals should clarify the relative roles of congregate housing, social settings, correctional care facilities, and other settings in contributing to the high rates of ongoing transmission that have occurred in these communities. The updated statement on controlling tuberculosis in the United States, published jointly in 2005 by the American Thoracic Society, Centers for Disease Control and Prevention, and the Infectious Disease Society of America (5), provided a list of major challenges to tuberculosis elimination. The challenges of particular importance for the inner-city populations, such as described in Texas (1), are delays in detection and reporting of cases of active pulmonary tuberculosis and deficiencies in protecting contacts and preventing outbreaks (5). Delays in seeking medical care and/or delays in clinical diagnosis for even a single individual with infectious tuberculosis in a homeless shelter can produce a major tuberculosis outbreak (6), and mandatory tuberculosis screening appears to be an effective means for reducing tuberculosis morbidity and transmission among homeless shelter residents (7, 8). The control statement also delineates key tuberculosis control roles for all medical practitioners, organizations, and institutions involved in caring for individuals at risk for tuberculosis. The report by Moonan and colleagues (1) provides a valuable illustration of the important roles public health departments have in identification of high-risk groups and the education of the high-risk populations and their respective community-based organizations. This article also illustrates the key tuberculosis control roles that community-based organizations, in partnership with public health departments, will need to play if tuberculosis is to be eliminated in high-risk populations (5). FOOTNOTES Conflict of Interest Statement: R.R. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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