Tuberculosis — United States, 1993–2010

Awal D. Khan, PhD, Elvin Magee, MPH, Gail Grant

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC

Corresponding author: Awal D. Khan, PhD, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC. Telephone 404-639-6272; E-mail: AKhan2@cdc.gov.

Introduction

Tuberculosis (TB) is transmitted via the airborne route by person-to-person contact. Although TB is a leading cause of death on a global scale (1), most cases can be cured with treatment. From 1993 to 2010, the number of TB cases reported in the United States decreased from 25,103 to 11,182. Despite the decrease, TB continues to affect many communities in the United States disproportionately and unequally, especially racial/ethnic minorities and foreign-born persons (2). TB remains one of many diseases and health conditions with large disparities and inequalities by income, race/ethnicity, educational attainment, and other sociodemographic characteristics (3).

This report is part of the second CDC Health Disparities and Inequalities Report (CHDIR). The 2011 CHDIR (4) was the first CDC report to assess disparities across a wide range of diseases, behavioral risk factors, environmental exposures, social determinants, and health-care access. The topic presented in this report is based on criteria that are described in the 2013 CHDIR Introduction (5). This report provides new information on TB, a topic not covered in the 2011 CHDIR. The purposes of this TB report are to discuss and raise awareness of differences in the characteristics of people who have TB in the United States and to prompt actions to reduce these disparities.

Methods

Tuberculosis (TB) is a disease caused by bacteria that is spread from person to person through the air when a TB sufferer coughs, sneezes, speaks, sings, or laughs. TB usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, or the spine. This analysis included all TB cases, and no cases or latent TB infection (LTBI). To assess disparities in newly reported cases of TB disease among persons of all ages in the United States, CDC analyzed 1993–2010 data from the National TB Surveillance System (NTSS). TB is a nationally notifiable disease (2). Since 1953, state and local health departments have submitted information to CDC on each newly reported case of TB disease in the United States. Currently, all 50 U.S. states and the District of Columbia (DC) as well as Puerto Rico, the U.S. Virgin Islands, and six other jurisdictions in the Pacific region (American Samoa, the Commonwealth of the Northern Mariana Islands, the Federated States of Micronesia, Guam, the Republic of the Marshall Islands, and the Republic of Palau) report information on newly diagnosed TB cases electronically using NTSS. The Report of a Verified Case of TB (RVCT) form (http://ftp.cdc.gov/pub/software/tims/2009%20rvct%20documentation/rvct%20training%20materials/rvct%20instruction%20manual.pdf), which was released in 1993, was expanded to collect additional information for each case, including human immunodeficiency virus (HIV) status, occupation, and history of substance abuse, homelessness, and drug susceptibility test results (2). Subsequent revisions of the RVCT form in 2009 include risk factors (e.g., diabetes, end-stage renal disease, and contact with a drug-resistant person), residential status, immigration status, and reasons for longer than usual TB therapy.

This report examines the number of TB cases and rates during 2006 and 2010 by patient-reported sex at birth, race/ethnicity, country of birth, patient primary occupation, employment status, number of years patient has been living in the United States, and type of health-care provider. Race was defined as white, black, Asian/Pacific Islander, and American Indian/Alaska Native. Ethnicity was defined as Hispanic and non-Hispanic. A person was considered U.S.-born or foreign-born on the basis of definitions used in the 2010 TB surveillance report (2). For employment status, a person was considered unemployed if not employed during the 12 months preceding TB diagnosis. During 1993–2008, occupation was assessed for the previous 2 years and multiple choices were accepted, but starting in 2009, occupation was assessed for 1 year before and multiple choice answers were no longer accepted. Geographic region was not analyzed because, in 2010, approximately half (49.2%) of all TB cases were concentrated in a small number of states (California, Florida, Texas, and New York), in which 67.5% of cases occurred in foreign-born persons (2).

Trends in TB rates during 1993–2010 by race/ethnicity and cases by country of birth are presented. TB case rates per 100,000 population and by sex and race/ethnicity were calculated using population estimates from the U.S. Census Bureau's Federated Electronic Research, Review, Extra, and Tabulation Tool (DataFerrett version 1.3.3), which were available during 2006–2010. The 2010 Current Population Survey was used to obtain population estimates stratified by country of birth (6). Disparities were measured as deviations from a "referent" category rate or percentage. Referent categories were selected because they demonstrated the most favorable group estimates for the variables used to assess disparities during 2006 and 2010 (7–8). For example, non-Hispanic white was selected as the referent category for the racial/ethnic variable. Absolute difference was measured as the simple difference between a group estimate and the estimate for its respective reference category, or referent group. Relative difference, a percentage, was obtained by dividing the absolute difference by the value in the referent category and multiplying by 100. To evaluate changes in disparity over time, relative differences for the groups in 2006 were subtracted from relative differences in 2010. No statistical testing was performed.

Results

During 2006–2010, a total of 62,642 verified TB cases were reported to CDC's NTSS from the 50 states, DC, Puerto Rico, the U.S. Virgin Islands, and six other jurisdictions in the Pacific region. Of these, 13,732 were reported in 2006 and 11,182 were reported in 2010. The national TB case rate was 4.6 cases per 100,000 population in 2006 and 3.6 cases per 100,000 population in 2010, a 20% decline over 5 years. The rate for males was 5.8 in 2006 and 4.5 in 2010.

The relative difference between males and females in reported TB rates was 70.6% in 2006 and 66.7% in 2010 (Table). From 2006 to 2010, the changes in relative differences for the various age groups were as follows: persons aged 15–24 years (22.9%), persons aged 25–44 years (40.0%), persons aged 45–64 years (44.3%), and persons aged ≥65 years (35.7%) (Table). In 2010, the relative difference between persons aged ≥65 years and the referent group was 450%.

From 2006 to 2010, all racial/ethnic minorities experienced decreases in TB case rates (Table). In 2006, Hispanics had case rates of 9.2 per 100,000, compared with 6.5 in 2010. Asians/Pacific Islanders had a rate of 26.1 in 2006 and 22.4 in 2010. Compared with whites, TB rates in 2010 were approximately seven times higher among Hispanics, eight times higher among blacks, and 25 times higher among Asians/Pacific Islanders.

During 2006–2010, 59% of 62,642 reported TB cases occurred among foreign-born persons. In 2006, the relative difference among foreign-born persons compared with U.S.-born persons was 857% and in 2010, the relative difference in reported TB rates among foreign-born persons compared with U.S.-born persons was 1,031%. The change in the relative difference from 2006 to 2010 was 175% (1,031% versus 856.5%, respectively) (Table).

Although racial/ethnic relative differences in TB case rates were similar in both U.S.-born and foreign-born persons, the magnitude of the relative disparities varied markedly between U.S.-born and foreign-born persons and was three-to-four times greater among foreign-born persons. In U.S.-born persons in 2010, the relative difference in TB rates compared with whites was 614% for blacks, 429% for Asians/Pacific Islanders, 286% for Hispanics, and 757% for American Indians/Alaska Natives (Table). Among foreign-born persons in 2010, the relative difference in TB rates compared with whites was 2,271% for Asians/Pacific Islanders, 1,771% for blacks, and 836% for Hispanics.

Among 6,748 foreign-born persons in the United States during 2010 with reported TB, approximately 21% received a diagnosis of TB disease within <2 years of arrival in the United States, approximately 18% within 2–5 years of arrival, and 50% in >5 years after arrival; an additional 11% had no information on arrival dates. The relative difference in TB cases diagnosed >5 years after arrival in the United States compared with cases diagnosed 2–5 years after arrival was 178.8% in 2010. The change in the relative difference between 2006 to 2010 for TB cases diagnosed >5 years after arrival in the United States was 41% (136.3% vs. 177.8%, respectively) (Table).

The proportion of TB cases among unemployed persons was 53% (7,245 of 13,732) in 2006 and 59% (6,217 of 10,520) in 2010. During 2010, the relative difference in reported TB cases among unemployed persons compared with those employed in fields other than health care (referent) was 74%. a change in the relative difference of 44.2% over time (Table).

The relative difference in reported TB cases among persons whose primary health-care provider for TB disease was a health department compared with persons whose primary health-care provider for TB disease was private/other providers (referent category) was 217% a change in the relative difference of 109% over time (326.3% in 2006 and 216.7% in 2010) (Table). The proportion of TB cases treated at health departments was 81% (10,830 of 13,308) in 2006 and 76% (4,587 of 6,011) in 2010.

From 1993 to 2010, TB case rates declined by approximately 63% (Figure 1). TB rates for Asians/Pacific Islanders were 41.2 per 100,000 population in 1993 and 22.4 per 100,000 in 2010, with differences in rates of 45.6%. From 1993 to 2010, among blacks, the rates ranged from 28.5 to 7.0 per 100,000 population, among Hispanics from 19.9 to 6.5, among American Indians/Alaska Natives from 14.0 to 6.4, and among non-Hispanic whites from 3.6 to 0.9.

From 1993 to 2010, the proportion of TB cases among foreign-born persons increased from 29% to 60% (Figure 2). From 1993 to 2010, the TB case rate in the United States has declined annually in both U.S.-born and foreign-born persons; overall, TB cases have declined 78% among U.S.-born persons compared with 47% among foreign-born persons.

In 1993, approximately 69% of reported TB cases occurred among U.S.-born persons (7.4 cases per 100,000) and 29% occurred among foreign-born persons (34.0 cases per 100,000). In comparison, during 2006–2010, on average, approximately 59% of reported TB cases occurred among foreign-born persons and remained relatively stable, and the rates of cases reported were 1.9 per 100,000 for U.S.-born and 22.0 for foreign-born persons.

Discussion

The number of new TB cases reported in the United States in 2010 represented an 87% decrease since reporting began in 1953 and a 58% decrease since the peak resurgence of TB reported in 1992 (2). Despite the downward trend, TB continues to affect many U.S. racial/ethnic minorities disproportionately, both U.S.-born and foreign-born. Approximately half of new TB cases in the United States occur among foreign-born persons and the TB rate in foreign-born persons was approximately 10 times that of persons born in the United States. This disparity has become more recognizable since 1993, when surveillance was enhanced to include routine collection of country of birth information (9). The foreign-born population presents a challenge to health-care staff and TB programs for providing diagnosis and care, and these challenges include the unequal prevalence of TB risk factors and barriers to access to TB care.

Several factors contribute to the disproportionate prevalence of TB among racial/ethnic and foreign-born minorities. Persons who were born in countries where TB morbidity is high might have acquired TB before immigrating and not have symptoms of active TB disease until after arrival in the United States. Different social and environmental living conditions create large and predictable differences in health outcomes among nations and between population groups within nations (10). In the United States, adjusting for six socioeconomic indicators (i.e., crowding, income, poverty, public assistant, education, and unemployment), low socioeconomic status accounted for approximately half of the increased risk for TB among blacks, Hispanics, and Native Americans (11). Unequal prevalence of TB risk factors (e.g., HIV infection, homelessness, incarceration, substance use, and TB disease severity) among racial/ethnic groups also might contribute to increased exposure to TB or to an increased risk for developing TB once infected. Economically disadvantaged persons, the uninsured, low-income children, the elderly, the homeless, those with HIV, and those with other chronic health conditions (e.g., diabetes and severe mental illness) encounter barriers to accessing health-care services. The effects of these barriers on TB prevention and control vary across racial/ethnic groups (12–14). In addition, poverty, language barriers, and immigration status also can be additional barriers to ameliorating TB disparities and inequality, jointly or independently (15–17).

Controlling and preventing TB in the United States necessitates addressing disparities among racial/ethnic minorities and foreign-born persons. The continuous arrival of new immigrants and refugees from countries with a high prevalence of TB has impeded elimination efforts. Reduction in TB rates among foreign born communities can be accomplished by identification of local at-risk populations, increased knowledge of issues affecting immigrants and foreign-born persons and modification of existing TB programs to meet the needs of these communities.  In particular, training and education can aid health-care staff serving the foreign-born community at risk for TB disease.

Limitations

The findings in this report are subject to at least four limitations. First, certain data (e.g., race/ethnicity and years in the United States) were incomplete and did not include U.S. territories and the U.S.-affiliated Pacific Islands. Second, the analysis does not assess the effects of socioeconomic risk factors (e.g., homelessness, substance abuse, and incarceration), HIV coinfection, and drug resistance on TB disparities. The prevalence of certain risk factors is particularly extensive in minority groups (e.g., persons with HIV/AIDS and diabetes). Third, educational attainment and family or household income, two indicators used commonly to explain health disparities and inequalities, were not available. Finally, social aspects that include language barriers and cultural differences with respect to health-seeking behaviors and the ability to access the complex U.S. health-care system were not examined.

Conclusion

Progress toward TB elimination in the United States will require ongoing surveillance and improved TB control and prevention activities to address persistent disparities between U.S.-born and foreign-born persons and between whites and racial/ethnic minorities. Disparities and inequalities among racial/ethnic minorities are affected by many unmeasured factors. CDC recommends improving awareness, testing, and treatment of latent infection and TB disease in minorities and foreign-born populations to reduce TB (9).

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