Original articleIndividual- and neighborhood-level contextual factors are associated with Mycobacterium tuberculosis transmission: genotypic clustering of cases in Michigan, 2004–2012
Introduction
Although the overall incidence of tuberculosis (TB) has been declining in the United States, stark disparities persist in the distribution of disease, particularly by race and nativity. Asian and Pacific Islanders (AI/PI) continue to have the highest incidence of TB in the United States and show no evidence of closing the gap with whites, whose incidence is lowest [1], [2]. Moreover, the rate of decline in TB incidence has recently begun to stagnate [3], particularly among foreign-born populations [4], and in both urban and rural populations [5], [6].
From a clinical perspective, measures of individual immune status and infectiousness are key to predicting transmission of Mycobacterium tuberculosis (MTB) [7]: individuals with underlying comorbidities, those with a positive sputum-smear, and those with abnormal chest radiography results are more likely to be associated with recent transmission. However, previous studies have also found both individual-level and neighborhood-level sociodemographic factors to be predictors of recent TB transmission. Individual-level sociodemographic characteristics such as younger age [8], [9], [10], minority race/ethnicity status [8], [11], male sex [9], [10], and being native-born [8], [11], [12], [13] have been associated with recent TB transmission. In addition, “known TB risk factors” as defined by the Centers for Disease Control and Prevention (CDC) surveillance forms [14], such as homelessness [8], [9], [13], incarceration [8], and drug use [13] have also been linked to recent transmission. Neighborhood-level studies have demonstrated that area-based measures of disadvantage are associated with increased incidence and transmission of TB, a finding particularly pronounced for those who are U.S.-born [15]. Several studies have also suggested the predictors of recent transmission are different for foreign-born and U.S.-born populations [16], highlighting the importance of investigating these two groups separately.
In 2012, Michigan had an annual incidence rate of 1.28 TB cases per 100,000 [17], notably lower than the U.S. national average incidence of 3.2 per 100,000 [4]. Despite Michigan's lower incidence, there is evidence of persistent disparities in TB risk, particularly by race and nativity [17]. Using TB surveillance data collected by the Michigan Department of Health and Human Services (MDHHS), we evaluated risk factors for recent transmission at both the individual- and neighborhood-levels among U.S.-born and foreign-born populations separately.
Section snippets
Study population and data collection
Our study subsample included only those cases with complete genotype data, both spacer oligonucleotide (spoligotype) and 12-locus-mycobacterial interspersed repetitive unit–variable number tandem repeat typing (MIRU-VNTR) results, and address information. The genotyping data are part of the CDC-based National Tuberculosis Genotyping Service [18]. Cases were excluded if they had incomplete genotyping data and/or were missing address information. The state of Michigan employs universal genotyping
Characteristics of the study population
A total of 1800 cases of TB were reported in Michigan from January 1, 2004 to December 31, 2012 (Supplementary Fig. 1). The final study sample consisted of 1236 cases, representing 69% of the 1800 total cases reported by MDHHS during this time period (Table 1). The racial/ethnic composition of these cases was 23% non-Hispanic white, 40% non-Hispanic black/African American, 25% Asian, 10% Hispanic, and 2% other. Most cases (72%) were between the ages of 18 and 64 years. The gender distribution
Discussion
We evaluated risk factors for recent transmission at both the individual and neighborhood levels among U.S.-born and foreign-born populations separately using a combination of genotyping and surveillance data from 1236 new TB cases reported in Michigan during 2004 through 2012.
Using time-restricted genotypic clusters as the proxy for recent transmission, we found significant differences between the U.S.-born and the foreign-born in the proportion of cases attributable to recent transmission.
Conclusions
Our findings point to the need for considering socioeconomic context in designing interventions aimed at reducing MTB transmission. Although a focus on individual-level factors in TB control may have reduced overall TB incidence in the United States during the last decades, our results suggest that this is insufficient to address enduring disparities in TB incidence that are largely patterned by social and economic disadvantages. Reducing disparities in TB incidence will require strategies that
Acknowledgments
The authors thank their collaborators at the TB Control Program at the Michigan Department of Health and Human Services for their contribution to the collection of the data used for this study. Dr. Noppert received partial support from the University of Michigan Rackham Graduate School and NIA grant 5 T32-AG000029-40.
References (38)
- et al.
Factors associated with genotype clustering of Mycobacterium tuberculosis isolates in an ethnically diverse region of southern California, United States
Infect Genet Evol
(2012) - et al.
Tuberculosis Genotyping Information Management System: Enhancing Tuberculosis Surveillance in the United States
Infect Genet Evol
(2012) Residential segregation and the epidemiology of infectious diseases
Soc Sci Med
(2000)Online tuberculosis information system, National Tuberculosis Surveillance System, 1993-2009
(2014)- et al.
Tuberculosis in indigenous peoples in the U.S., 2003-2008
Public Health Rep
(2011) - et al.
Leveling of Tuberculosis Incidence—United States, 2013–2015
MMWR Morb Mortal Wkly Rep
(2016) - CDC, Division of Tuberculosis Elimination, Trends in Tuberculosis—United States, 2013. MMWR Morb Mortal Wkly Rep 6th...
- et al.
The Road to Tuberculosis (Mycobacterium tuberculosis) Elimination in Arkansas; a Re-Examination of Risk Groups
PLoS One
(2014) - et al.
Epidemiology of Urban Tuberculosis in the United States, 2000–2007
Am J Public Health
(2011) Core curriculum: what the clinician should know - TB
(2013)
Identifying areas and risk groups with localised Mycobacterium tuberculosis transmission in northern England from 2010 to 2012: spatiotemporal analysis incorporating highly discriminatory genotyping data
Thorax
Mycobacterium tuberculosis transmission in a country with low tuberculosis incidence: role of immigration and HIV infection
J Clin Microbiol
Impact of immigration on the molecular epidemiology of tuberculosis in Rhode Island
J Clin Microbiol
Using genotyping and geospatial scanning to estimate recent mycobacterium tuberculosis transmission, United States
Emerg Infect Dis
Geo-epidemiologic and molecular characterization to identify social, cultural, and economic factors where targeted tuberculosis control activities can reduce incidence in Maryland, 2004-2010
Public Health Rep
Neighborhood socioeconomic position and tuberculosis transmission: a retrospective cohort study
BMC Infect Dis
Clustered tuberculosis in a low-burden country: nationwide genotyping through 15 years
J Clin Microbiol
Race and nativity are major determinants of tuberculosis in the US: evidence of health disparities in tuberculosis incidence in Michigan, 2004-2012
BMC Public Health
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Present affiliation: Center for the Study of Aging and Human Development, Duke University, 201 Trent Dr. Durham, NC 27710; email: [email protected].