Trends in Tuberculosis Incidence --- United States, 2006

In 2006, a total of 13,767 tuberculosis (TB) cases (4.6 per 100,000 population) were reported in the United States, representing a 3.2% decline from the 2005 rate. This report summarizes provisional 2006 TB incidence data from the National TB Surveillance System and describes trends since 1993. The TB rate in 2006 was the lowest recorded since national reporting began in 1953, but the rate of decline has slowed since 2000. The average annual percentage decline in the TB incidence rate decreased from 7.3% per year during 1993--2000 (95% confidence interval [CI] = 6.9%--7.8%) to 3.8% during 2000--2006 (CI = 3.1%--4.5%). Foreign-born persons and racial/ethnic minority populations continue to be affected disproportionately by TB in the United States. In 2006, the TB rate among foreign-born persons in the United States was 9.5 times that of U.S.-born persons.* The TB rates among blacks, Asians, and Hispanics^† were 8.4, 21.2, and 7.6 times higher than rates among whites, respectively. The slowing of the decline in the overall national TB rate and the inability to effectively address persistent disparities in TB rates between U.S.-born and foreign-born persons and between whites and racial/ethnic minority populations threaten progress toward the goal of eliminating TB in the United States. In 1989, CDC and the Advisory Committee for the Elimination of Tuberculosis issued a strategic plan for the elimination of TB, setting an interim target case rate of 3.5 per 100,000 population by 2000 and ultimately the elimination of TB (i.e., <1 case per 1 million population) in the United States by 2010 (1).

TB is a nationally notifiable disease. Health departments in the 50 states and District of Columbia (DC) electronically report to CDC any TB cases that meet the CDC and Council of State and Territorial Epidemiologists case definition.^§ Reports include the patient's race, ethnicity (i.e., Hispanic or non-Hispanic), treatment information, and drug-susceptibility test results if available. For this analysis, CDC calculated national and state TB rates (2) and rates for foreign-born and U.S.-born persons (3) and racial/ethnic populations (4) by using current U.S. census population estimates for the years 1993 through 2006.

In 2006, TB incidence rates in the 51 reporting areas ranged from 0.8 (Wyoming) to 12.6 (DC) cases per 100,000 population (median: 3.4 cases). Thirty states had lower rates in 2006 than 2005; 20 states and DC had higher rates (Table 1). In 2006, for the second consecutive year and the second time since national reporting began, approximately half of states (26 of 50) had TB rates of <3.5 per 100,000 (Figure 1); however, 11 of those 26 states had higher rates of TB in 2006 than in 2005. Seven states (California, Florida, Georgia, Illinois, New Jersey, New York, and Texas) reported more than 500 cases each for 2006; combined, these seven states accounted for 60% (8,259) of all TB cases.

Among U.S.-born persons, the number and rate of TB cases continued to decline in 2006. The U.S.-born TB rate was 2.3 per 100,000 population (5,924 or 43.3% of all cases with known origin of birth), representing a 7.0% decline in rate since 2005 and a 68.6% decline since 1993 (Figure 2).

Among foreign-born persons, the number of TB cases increased in 2006, but the rate decreased. The foreign-born TB rate in 2006 was 21.9 per 100,000 population, representing a 0.5% decline in rate since 2006 and a 35.8% decline since 1993. As the rate of decline in TB cases among foreign-born persons lagged behind the decline in TB cases among U.S.-born persons, the foreign-born to U.S.-born rate ratio increased 7.0%, from 8.9 in 2005 to 9.5 in 2006. In 2006, approximately half (55.6%) of TB cases among foreign-born persons were reported in persons from five countries: Mexico (1,912), the Philippines (856), Vietnam (630), India (540), and China (376).

In 2006, for the third consecutive year, more TB cases were reported among Hispanics than any other racial/ethnic population. Among persons with TB whose country of birth was known, 95.6% (3,126 of 3,269) of Asians, 74.7% (3,024 of 4,050) of Hispanics, 29.9% (1,110 of 3,712) of blacks, and 17.8% (427 of 2,404) of whites were foreign born. From 2005 to 2006, TB rates declined for all racial/ethnic minorities except American Indians/Alaska Natives and Native Hawaiians or Other Pacific Islanders^¶ (Table 2).

Human immunodeficiency virus (HIV) contributes to the TB pandemic because immune suppression increases the likelihood of rapid progression from TB infection to TB disease. From 2005 to 2006, among TB cases with HIV status reported,** the percentage of TB cases with HIV infection decreased 4.4% (from 13.0% to 12.4%), but the percentage of TB cases with unknown HIV status increased 10.3% (from 28.7% to 31.7%).^†† The decline in the percentage of TB cases with HIV infection might reflect incomplete reporting of HIV test results attributed to a lack of HIV testing or HIV reporting.

A total of 124 cases of multidrug-resistant TB (MDR TB)^§§ were reported in 2005, the most recent year for which complete drug-susceptibility data are available.^¶¶ The proportion of MDR-TB cases remained constant at 1.2% from 2004 (129 of 10,846 TB cases) to 2005 (124 of 10,662). In 2005, MDR TB continued to disproportionately affect foreign-born persons, who accounted for 101 (81.5%) of 124 MDR-TB cases.

The recommended length of drug therapy for most types of TB is 6--9 months. In 2003, the latest year for which treatment data are complete, 82.7% of patients for whom <1 year of treatment was indicated completed therapy within 1 year, below the Healthy People 2010 target of 90% (objective 14-12).

Reported by: R Pratt, V Robison, T Navin, Div of TB Elimination, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (proposed); M Hlavsa, E Pevzner, EIS officers, CDC.

Editorial Note:

Since the resurgence of TB in the United States during 1985--1992, the annual TB rate has decreased steadily. However, the rate of decrease has slowed. Furthermore, the proportion of TB cases among foreign-born persons has increased each year since 1993. If the global TB pandemic remains unmitigated, eliminating TB in the United States will be increasingly difficult because most foreign-born persons in the United States who progress from latent TB infection to TB disease initially became infected with TB abroad.

To address the higher rate of TB among foreign-born persons in the United States and the increasing proportion of cases they represent, CDC is considering several strategies (e.g., revising overseas medical screening of applicants for U.S. immigration). These strategies should decrease importation of TB into the United States and improve immigrant and refugee health. CDC also is continuing to work with international partners, including the Stop TB Partnership (http://www.stoptb.org), to strengthen TB control in countries with high TB incidence.

To address the disproportionately high rate of TB in the United States among Asians and Hispanics, CDC is working with international health organizations to help reduce TB in affected countries. To help address the disproportionately high rate of TB among blacks in the United States, in May 2006, the CDC and Research Triangle Institute International convened the Stop TB in the African-American Community Summit to focus attention on the problem of TB in the black community (http://www.cdc.gov/nchstp/tb/tbinafricanamericans).

In 2005 and 2006, reported HIV status (i.e., positive or negative test result) was not available for nearly one third of TB cases reported in the United States. HIV is the most important known risk factor for progression from latent TB infection to TB disease (5). Patients with TB and HIV are five times more likely to die during anti-TB treatment than patients not infected with HIV, underscoring the importance of early diagnosis and treatment for TB/HIV coinfection (6). In 2006, CDC issued new guidelines recommending that all patients initiating treatment for TB be screened routinely for HIV infection (7). CDC also is working to increase awareness of TB/HIV coinfection domestically among health-care providers through educational resources and training courses developed by CDC's TB Regional Training and Medical Consultation Centers in collaboration with the Health Resources and Services Administration.

The need for new anti-TB drugs was emphasized in 2006 by identification of a cluster of extensively drug-resistant TB cases among HIV-infected persons in a rural area of KwaZulu-Natal, South Africa (8). Progress has been made on several new drugs in the past year. Six agents in five different drug classes are being tested in humans (TMC-207, OPC 67683, SQ109, PA824, moxifloxacin, and gatifloxacin). In collaboration with the Global Alliance for TB Drug Development, CDC's TB Trials Consortium (TBTC) has completed two preliminary trials with moxifloxacin. These trials will help lay the groundwork for a trial of a treatment-shortening regimen for TB. TBTC also is nearing completion of a trial of a 3-month rifapentine-based treatment for latent TB infection.

Despite these targeted measures to control TB, the slowing of the decline in the TB rate indicates a need for improved case management and contact investigation, intensified outreach and testing of populations at high risk, better treatments and diagnostic tools, improved understanding of TB transmission, and continued collaborative measures with other nations to reduce TB globally. These measures are required to fully implement the Institute of Medicine's recommendations for eliminating TB in the United States (9).

Acknowledgments

The findings in this report are based, in part, on data contributed by state and local TB-control officials.

References

1. CDC. A strategic plan for the elimination of tuberculosis in the United States. 1989. MMWR 1989;38(No. S-3).
2. US Census Bureau. Annual estimates of the populations for the United States and states, and for Puerto Rico. Washington, DC: US Census Bureau; 2007. Available at http://www.census.gov/popest/estimates.php.
3. US Census Bureau. Current population survey. Annual estimates of the United States foreign-born and native resident populations. Washington, DC: US Census Bureau; 2007. Available at http://dataferrett.census.gov.
4. US Census Bureau. National population estimates---characteristics: national sex, age, race, and Hispanic origin. Washington, DC: US Census Bureau; 2007. Available at http://www.census.gov/popest/datasets.html.
5. CDC. Prevention and treatment of tuberculosis among patients infected with human immunodeficiency virus: principles of therapy and revised recommendations. MMWR 1998;47(No. RR-20):1--58.
6. McCombs SB. Tuberculosis mortality in the United States, 1993--2001. Presented at CDC Division of Tuberculosis Elimination Seminar, Atlanta, GA; December 2003.
7. CDC. Revised recommendations for HIV testing of adults, adolescents, and pregnant women in health-care settings. MMWR 2006; 55(No. RR-14).
8. CDC. Emergence of Mycobacterium tuberculosis with extensive resistance to second-line drugs---worldwide, 2000--2004. MMWR 2006; 55:301--5.
9. Geiter L, ed. Ending neglect: the elimination of tuberculosis in the United States. Washington, DC: National Academies Press; 2000.

* A U.S.-born person was defined as someone born in the United States or its associated jurisdictions or someone born in a foreign country but having at least one U.S.-born parent. Persons not meeting this definition were classified as foreign born. For 2006, persons with unknown origin of birth represented 0.6% (84 of 13,767) of total cases.

^† For this report, persons identified as white, black, Asian, American Indian/Alaska Native, Native Hawaiian or Other Pacific Islander, or of multiple race are all classified as non-Hispanic. Persons identified as Hispanic might be of any race.

^§ Full case definition is available at http://www.cdc.gov/epo/dphsi/casedef/tuberculosis_current.htm. To be considered a confirmed case, cases must meet the clinical case definition or be laboratory confirmed. Cases are not counted twice within any consecutive 12-month period. However, cases in which the patient had previously verified disease are reported again if the patient was discharged from treatment. Cases also are reported again if the patient was lost to supervision for >12 months and disease can be verified again.

^¶ Reporting of official CDC TB statistics for race/ethnicity changed beginning in 2003. A "Native Hawaiian or Other Pacific Islander" category was added to the race/ethnicity reporting options, and multiple races also could be reported for a given patient.

** For this report, California was excluded from the analysis of HIV among TB cases because it reports its HIV data separately from its TB data and 1 year behind all other states. HIV data reported by California only includes the number of patients with TB that are HIV positive. The number of patients testing negative, refusing testing, or not offered testing is not reported. Therefore, determining the percentage of patients with a known HIV status for California is not possible because patients are classified as HIV positive or unknown.

^†† For this report, the "known HIV status" category is based on the number of cases with reported "positive" or "negative" status. The "unknown HIV status" category is based on "indeterminate," "refused," "not offered," "test performed but status unknown," "unknown," and "data missing" categories. In 2006, HIV status was classified as "data missing" for 0.9% of TB cases (101 of 10,986 TB cases, excluding California). All HIV estimates were based on provisional data.

^§§ Defined as a case of TB in a person with a Mycobacterium tuberculosis isolate resistant to at least isoniazid and rifampicin.

^¶¶ Drug-susceptibility testing for isoniazid and rifampicin was performed for 98.3% (11,132 of 11,325) and 97.4% (10,662 of 10,946) of culture-confirmed cases of M. tuberculosis in 2004 and 2005, respectively.

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Date last reviewed: 3/22/2007