Tuberculosis and the Asian Population of Tarrant County, Texas

Abstract: 

The research in this paper examines the incidence of tuberculosis (TB) among foreign-born Asians living in Tarrant County, Texas. According to the Centers for Disease Prevention and Control (CDC), TB in native-born Americans is steadily decreasing, while remaining constant for the foreign-born. In 2007, the TB rate among the foreign-born was 9.7 times that of U.S.-born, but among Asians it was 22.9 times the rate among Whites (CDC 2008 September). Data for this study were taken from a tuberculosis screening program conducted in Tarrant County from 1993 to 2006. Using Geographic Information System and statistical analysis, the study explores the relative contribution of traditional epidemiological factors including crowdedness, poverty, and less common factors such as self-reported incarceration, drug use, and other risky behaviors. The results indicate that although Asians make up 4.2% of the population, they account for 18% of TB cases. Surprisingly, however, Asians with TB are less likely to participate in the traditional high-risk behaviors that are normally associated with tuberculosis, including drug use (Χ2 = 57.426, p = .000), alcoholism (Χ2 = 39.776, p = .000), homelessness (Χ2 = 37.029, p = .000), and previous incarceration (Χ2 = 27.359, p =. 000). Traditional programs targeting such high-risk populations may exclude Asians and thus threaten the progress toward TB elimination in the United States (CDC 2008 September). Targeted programs are needed to control TB in the Asian community to facilitate the elimination of TB in the United States.

Table of Contents: 

    Introduction

    Tuberculosis (TB) in native-born Americans declined from 1993 to 2007, but foreign-born persons and racial/ethnic minority populations continue to be affected disproportionately (CDC 2008 March) (Figure 1). In 2007, the TB rate among foreign-born persons was 9.7 times that of U.S.-born persons; the TB rates among Blacks, Asians, and Hispanics were 8.3, 22.9, and 7.4 times higher respectively than rates among Whites (CDC 2008 September). This research examines the factors that may account for TB rates in the Asian population in comparison to other ethnic groups in Tarrant County. The question is whether traditional high-risk behaviors such as drug use, alcoholism, and homelessness are responsible for the high rates of TB among Asians.

    Texas has one of the highest rates of TB in the United States (CDC 2008 March). According to a report by the Centers for Disease Control and Prevention (CDC 2008 September) in 2007, 29 states lowered their individual rate of TB from 2006, whereas 21 states had higher rates. Of these states with increased rates, five contributed more than half of the total TB cases in the U.S. (CDC 2008 March). These five states included California, Florida, Illinois, New York, and Texas (CDC 2008 March). Tarrant County, one of the fastest growing urban counties in the U.S. today, also has one of the highest rates of TB in Texas (Tarrant County Public Health Department 2009; Texas Department of State Health 2006).

    Many factors are associated with increased rates of TB in certain populations. The CDC (2008 September) identifies high risk groups for TB to include homeless persons, persons residing in correctional facilities, injection drug users, and persons with substance abuse problems. These groups have high rates because they are frequently exposed and also have weaker immune systems which allow for TB to become active quickly, thus aiding in the transmission throughout the group.

    Prison communities are conducive for TB transmission because of their close quarters and common living facilities. It has been reported that the incidence among inmates in California state prisons in 1987 was 80.3 per 100,000, a rate nearly six times that of California’s general population for that year (CDC 1989). Thus, TB transmission in correctional facilities presents a health problem not only for correctional institutions, but also for the communities surrounding the facilities and communities into which the inmates are released (CDC 1989). Consequently, previous incarceration is an important risk factor for TB.

    TB transmission among immigrants into the U.S. is also a major problem. In fact, the CDC identifies people who have migrated from areas of the world with high rates of TB as a high risk group (CDC 2008 September). The Asian continent has particularly high rates of TB. According to the World Health Organization (2007) in 2007, the rate of new cases per 100,000 population was 98 for China, 171 for Vietnam, and 21 for Japan. These rates are extremely high compared to the rate of 4.2 in the United States. Due to these high rates, Asian origin may be an important risk factor.

    In the U.S. alone, the percentage of Asians with tuberculosis has risen 20% to 26% from 1998 to 2007 (CDC 2007). The CDC reports that from 2006 to 2007 the rate of TB in Blacks decreased by 8.4%, Whites decreased by 6.6%, Hispanics decreased by 8.6%, but Asians actually increased by 0.8% (CDC 2008 March). This shows that TB control efforts are succeeding among all major groups except Asians. It is important to understand why TB rates among Asians are not declining and to determine what can be done to fix the problem.

    Early detection is critical for interrupting TB transmission and improving the outcomes of individuals suffering from tuberculosis. Consequently, focusing surveillance and control activities on high risk areas and people promises to be a more effective strategy. Unfortunately, because the Asian population has not historically been identified as a high-risk population, they have not been targeted by screening and treatment programs.

    Finally, because political boundaries do not provide protection against communicable diseases such as TB, control efforts within the United States need to be linked with global efforts. Untreated TB among the foreign-born living in the United States creates a reservoir and a permanent source of new infections for the U.S.-born (Oppong, Denton, Moonan, and Weis 2007). This is evidence that it is impossible to eliminate TB in the United States until the disease is eliminated across the world. Targeting Asians with tuberculosis in the U.S. is an excellent starting point that will hopefully yield significant results. Consequently, it is important to know the major determinants of TB among Asians in order to plan effective interventions.

    Research Questions

    This paper begins this effort by addressing two main research questions.

    • Are traditional high-risk behaviors (e.g., alcohol abuse, drug use, homelessness, sexual behavior) responsible for the high rates of tuberculosis in Asians?
    • How does the Asian population’s participation in risky behaviors compare to other race/ethnic groups?

    Methodology

    Location-based targeted screening is the current recommended method for TB surveillance and control (CDC 2008 September). In a recent study, Moonan et al. (2004) developed the idea of using Geographic Information Systems (GIS) in combination with molecular surveillance. This study successfully collected data on individuals recently diagnosed with tuberculosis and used zip codes to plot where each case was located (Moonan et al. 2004). Using information from TB strain genotyping and GIS analysis, local public health officials were able to develop and initiate a highly successful tuberculosis control intervention (Reeves 2006). Data for this study were extracted from that larger study.

    The database, comprising 834 patients, was taken from a tuberculosis-screening program in Tarrant County, Texas, 1993-2006. As part of a CDC tuberculosis control effort, all newly diagnosed cases of TB were enrolled in the study. Each individual was asked a series of questions about their age, sex, race, place of birth, history of drug or alcohol abuse, sexual preference, and previous incarceration. Sputum samples were genotyped using appropriate methods including spoligotyping.

    Major Findings/Implications

    Figure 2 shows the distribution of TB rates in various Tarrant County zip codes. The areas closest to downtown have the highest rates of TB. Although Asians make up 4.2% of Tarrant County’s population, they contributed 18% of TB cases recorded. In contrast, Whites, comprising 56% of the population, reported 26% of total cases. TB is overrepresented among Asians in Tarrant County (Figure 3).

    Surprisingly, however, despite the high rates, Asians were less likely to participate in the high-risk behaviors that are traditionally associated with tuberculosis transmission, including drug use (Χ2 = 57.426, p = .000), alcoholism (Χ2 = 39.776, p = .000), homelessness (Χ2 = 37.029, p = .000), and previous incarceration (Χ2 = 27.359, p = .000) (Table 1). In non-Asians with TB, 30.7% were drug users in comparison with 1.3% of Asians (Table 2). There was a similar trend with diagnosed alcoholics: 30.8% of non-Asians with TB were diagnosed alcoholics in comparison to 6.5% of Asians. Homelessness was also much lower among Asians. Only 1.3% of Asians with TB had been homeless, whereas in the non-Asian TB population, 22.9% reported being homeless at some point in their lives. Consequently, traditional programs targeting such high-risk populations probably exclude or miss Asians with high rates of TB and may threaten the progress toward TB elimination in the United States (CDC 2008 March).

    The strain type a person carries is evidence of the possible source of infection (Oppong et al. 2007). People with similar strains indicate recent transmission, where one infected the other or the two were infected from a common source. A unique strain is evidence of remote transmission. Strain 210, the Beijing strain, is endemic to Tarrant County, and the strain carried by the majority of patients with TB in Tarrant County. Surprisingly, whereas 16.6% of the non-Asians had strain 210, zero percent of Asians in the study had strain 210. This suggests that most of these Asians probably acquired TB in their country of origin. The CDC reports that 96.1% of Asians with TB are foreign-born (CDC 2008 March). This is consistent with our sample, where 96% of Asians with TB are foreign-born. The data confirm evidence of remote transmission or infection from their country of origin.

    In the report on TB in Tarrant County posted on the Tarrant County Public Health Department’s website, Asians were not recognized as a specific ethnic group but were grouped with “Other.” Thus, TB prevalence was reported only for Whites, Blacks, Hispanics, and Other. The highest TB rate per 100,000 population was in the Other group with 27.6 cases in 2004 (Tarrant County Public Health Department 2009). This number is extremely high and cannot be controlled until the contributing groups of people are identified and targeted with surveillance, intervention, and control efforts. Asians in the U.S. may be a reservoir of TB and merit special intervention and control efforts.

    Conclusion and Discussion

    Asians account for a disproportional number of TB cases in Tarrant County; however, a majority of these Asians are not participating in the high-risk behaviors that are usually associated with TB. The explanation lies in the fact that 96% of the Asians with TB in our study were foreign-born. It appears that these Asian TB cases in the U.S. may be originating outside the United States, from Asia, an area known to have high rates of TB, and thus, reflect the health status and characteristics of their origin (Oppong et al. 2007). Also, the literature reviewed for this study has made it clear that there is a need for future research to examine the location and conditions affecting Asians in the United States. Specific target-programs are needed for the control of TB in the Asian community in order to facilitate TB elimination in the United States. As the recent swine flu outbreak, SARS, and the influenza mortality during 1918-1919 indicate, uncontrolled communicable disease in any part of the world threatens the entire human race.

    References

    • CDC. 2008, March 21. MMWR: Trends in Tuberculosis—United States, 2007 MMWR 57(11);281-285. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5711a2.htm (accessed July 14, 2009).
    • CDC. 2008, September. Reported tuberculosis in the United States, 2007. Atlanta, GA: U.S. Department of Health and Human Services, CDC. http://www.cdc.gov/tb/statistics/reports/2007/pdf/fullreport.pdf (accessed July 14, 2009).
    • CDC. 1989, May 12.Current trends prevention and control of tuberculosis in correctional institutions: Recommendations of the Advisory Committee for the Elimination of Tuberculosis. MMWR 38(18);313-320,325. <http://www.cdc.gov/mmwr/preview/mmwrhtml/00001388.htm> (accessed July 14, 2009).
    • CDC. 2007. Tuberculosis cases, percentages, and case rates per 100,000 population by race only: United States, 1993-2007.  http://www.cdc.gov/tb/statistics/reports/2007/pdf/fullreport.pdf (accessed July 14, 2009).
    • Moonan, Patrick K, Manuel Bayona, Teresa N Quitugua, Joseph Oppong, Denise Dunbar, Kenneth C Jost Jr, Gerry Burgess, Karan P Singh, and Stephen E Weis. 2004. Using GIS technology to identify areas of tuberculosis transmission and incidence. International Journal of Health Geographics 3:23.
    • Oppong J. R., Denton C. J., Moonan P. K., and Weis S. E.. 2007. Foreign-born status and geographic patterns of tuberculosis genotypes in Tarrant County, Texas. The Professional Geographer 59(4): 478 – 491.
    • “OTIS 2007 TB Data Results.” 2007. OTIS. CDC Wonder. http://wonder.cdc.gov/controller/datarequest/D38 (accessed July 14, 2009).
    • Reeves, R. 2006. Universal genotyping as a tool for establishing successful partnerships for tuberculosis elimination. American Journal of Respiratory and Critical Care Medicine 174: 491-492.
    • Tarrant County Public Health Department. 2009. Client Services: Tuberculosis, 2009. http://www.tarrantcounty.com/ehealth/cwp/view.asp?A=763&Q=430433 (accessed July 14, 2009).
    • Texas Department of State Health. Tuberculosis Statistics: 2006 TB Cases in Texas map. www.dshs.state.tx.us/idcu/disease/tb/statistics/ (accessed July 14, 2009).
    • WHO. 2007. Online Tuberculosis Database per Country. http://apps.who.int/globalatlas/predefinedReports/TB/index.asp?rptGrp=5 (accessed July 14, 2009).

    Table 1: Comparison of Participation in High-Risk Behaviors of Asian and Non-Asian Samples with Tuberculosis in Tarrant County, Texas, 1993-2006

     

    Non-Asian

    Asian

    Chi-Square

    Alcoholic

    Admitted

    Diagnosed

     

    128

    211

     

    3

    9

     

    26.732 (p=.000)

    39.776 (p=.000)

    Drug User

    IV Drug User

    Crack-Cocaine

    210

    78

    102

    2

    1

    1

    57.426 (p=.000)

    17.443 (p=.000)

    25.042 (p=.000)

    Sexual Behavior

    Sex w/HIV infected person

    Sex w/prostitute

    Sex w/homosexual

     

    98

    95

    32

     

    2

    8

    1

     

    20.780 (p=.000)

    9.342 (p=.000)

    5.694 (p=.058)

    Strain 210 (endemic to Tarrant County)

    114

    0

    28.723 (p=.000)

    Homeless

    157

    2

    37.019 (p=.000)

    Incarceration

    247

    23

    27.359 (p=.000)

    Table 2: Comparison of Percentages of Asians and Non-Asians with Tuberculosis in Tarrant County Who Participate in High-Risk Behavior, 1993-2006

     

    Non-Asian (%)

    Asian (%)

    Alcoholic

    Admitted

    Diagnosed

     

    18.7%

    30.8%

     

    2.0%

    6.5%

    Drug User

    IV Drug User

    Crack-Cocaine

    30.7%

    11.4%

    14.9%

    1.3%

    0.7%

    0.7%

    Strain 210

    16.6%

    0%

    Homeless

    22.9%

    1.3%

    Incarceration

    36.1%

    15.4%

    Figure 1: Comparison of the Number of Tuberculosis Cases in the United States among the U.S.-Born and Foreign-Born Populations, 1993-2007

    McCallister Jessica Figure 1

    Figure 2: Map Showing Tuberculosis Rates per 10,000 by Zip-Code Areas in Tarrant County Texas, 1993-2006

    McCallister Jessica Figure 2

    Figure 3: Map Showing Tuberculosis Rates Among Asians per 10,000 by Zip-Code Areas in Tarrant County Texas, 1993-2006

    McCallister Figure 3