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Trends in Tuberculosis --- United States, 2007
In 2007, a total of 13,293 tuberculosis (TB) cases were reported in the United States; the TB rate declined 4.2% from 2006 to 4.4 cases per 100,000 population. This report summarizes provisional 2007 data from the National TB Surveillance System and describes trends since 1993. The TB incidence rate in 2007 was the lowest recorded since national reporting began in 1953. Despite this overall improvement, progress has slowed in recent years; the average annual percentage decline in the TB rate slowed from 7.3% per year during 1993--2000 to 3.8% during 2000--2007.* Foreign-born persons and racial/ethnic minorities continued to bear a disproportionate burden of TB disease in the United States. In 2007, the TB rate in foreign-born persons in the United States was 9.7 times higher than in U.S.-born persons. TB rates among Hispanics,§ blacks, and Asians were 7.4, 8.3, and 22.9 times higher than among non-Hispanic whites, respectively. In 2007, foreign-born persons accounted for a majority of TB cases among Hispanics (77.2% [2,942 of 3,812]) and among Asians (96.1% [3,261 of 3,393]), whereas U.S.-born persons accounted for a majority of TB cases among blacks (71.2% [2,439 of 3,427]). Among U.S.-born racial and ethnic groups, the greatest disparity in TB rates was for U.S.-born blacks, whose rate remained nearly eight times that of U.S.-born whites.¶ The slowing decline in TB incidence and persistent disparities between U.S.-born and foreign-born persons and between whites and minorities threaten progress toward TB elimination in the United States. The strategic plan for the elimination of TB issued in 1989 by CDC and the Advisory Committee for the Elimination of Tuberculosis set a goal of TB elimination (i.e., less than one case per 1 million population) by 2010 and an interim target case rate of 3.5 per 100,000 population by 2000 (1).
Health departments in the 50 states and the District of Columbia (DC) electronically report to CDC verified TB cases that meet the CDC/Council of State and Territorial Epidemiologists case definition.** Reports include the patient's race, ethnicity (i.e., Hispanic or non-Hispanic), treatment information, and, whenever available, drug-susceptibility test results. CDC calculates national and state TB rates overall, by country of origin, and by racial/ethnic group by using current U.S. census population estimates (2--4).
In 2007, TB rates in reporting areas ranged from 0.4 (Wyoming) to 10.2 (DC) cases per 100,000 population (median: 3.5 cases). Twenty-nine states and DC had lower rates in 2007 than 2006; 21 states had higher rates. In 2007, for the third consecutive year and the third time since national reporting began, more than half of states (52.0% [26 of 50]) had TB rates less than or equal to the 2000 interim target case rate of 3.5 per 100,000 population (Figure 1); however, 12 (46.2%) of those 26 had higher rates of TB in 2007 than in 2006. Five states (California, Florida, Illinois, New York, and Texas) reported more than 500 cases each for 2007; combined, these five states accounted for more than half (52.0% [6,912]) of all TB cases.
Among U.S.-born persons, the number and rate of TB cases continued to decline in 2007. The number of TB cases in U.S.-born persons (5,464 [or 41.5% of all cases in persons with known origin]) declined 7.4% compared with 2006 and 68.6% compared with 1993 (Figure 2). In 2007, the TB rate among U.S.-born persons was 2.1 per 100,000 population, representing a 7.8% decline since 2006 and a 71.4% decline since 1993.
Among foreign-born persons in the United States, both the number and rate of TB cases declined in 2007. A total of 7,690 TB cases were reported among foreign-born persons (58.5% of all cases in persons with known origin), a 1.6% decrease from the 7,814 cases reported in 2006. The TB rate among foreign-born persons in 2007 was 20.6 per 100,000 population, which was a 6.5% decline since 2006 and a 39.5% decline since 1993. In 2007, more than half (51.8%) of foreign-born TB cases were reported in persons from four countries: Mexico (1,846), the Philippines (952), India (619), and Vietnam (568).
For the fourth consecutive year, more TB cases were reported among Hispanics than any other racial/ethnic group in 2007. From 2006 to 2007, TB rates declined for all racial/ethnic minorities except for Asians (+0.8%) and Native Hawaiian or other Pacific Islanders (+42.9%)§§ (Table).
In 2007, among persons with TB with a known human immunodeficiency virus (HIV) test result, 11.3% (869 of 7,708) were coinfected with HIV. California data were not included in this calculation.¶¶
A total of 116 cases of multidrug-resistant TB (MDR TB)*** were reported in 2006, the most recent year for which complete drug-susceptibility data are available. The proportion of MDR TB cases was 1.1% in 2006 (116 of 10,306), compared with 1.2% in 2005 (124 of 10,633). The proportion of MDR TB cases among persons without a previous history of TB has remained stable at approximately 1.0% since 1997, but has been approximately four to five times higher for persons with a previous history of TB. In 2006, MDR TB continued to disproportionately impact foreign-born persons, who accounted for 84.5% of MDR TB cases. Foreign-born persons had higher percentages of MDR TB, both among persons with (7.0%) and without (1.4%) a previous history of TB. Since drug-susceptibility reporting began in 1993, cases of extensively drug-resistant TB (XDR TB)§§§ have been reported every year in the United States except 2003. Two XDR TB cases were reported in 2005 and four in 2006. As of February 13, 2008, two XDR TB cases had been reported for 2007.
The recommended length of drug therapy for most types of TB is 6--9 months. In 2004, the latest year for which end-of-treatment data are complete, 82.1% of patients for whom <1 year of treatment was indicated completed therapy within 1 year, which is 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; H Menzies, EIS Officer, CDC.
After the resurgence of TB in the United States during 1985--1992, the annual TB rate decreased steadily. However, that decrease has now slowed. Furthermore, the proportion of TB cases contributed by foreign-born persons has increased each year since 1993. To achieve the goal of TB elimination in the United States (1), intensified efforts are required to strengthen domestic TB control and to address the global TB pandemic.
CDC is pursuing several strategies to address the higher rate of TB among foreign-born persons in the United States and the increasing proportion of cases they represent. In 2007, CDC published revised requirements for overseas medical screening of applicants for U.S. immigration (6,7). These revised technical instructions include 1) expanding TB screening by adding targeted tuberculin skin testing of children aged 2--14 years who live in countries with high TB incidence (i.e., WHO-estimated rates of >20 cases per 100,000 population) and all contacts of persons known to have TB, and 2) adding cultures and drug-susceptibility testing for persons with suspected TB.¶¶¶ Implementation of these new guidelines began in 2007 in Mexico, Nepal, the Philippines, and Thailand, and is scheduled to start in 2008 in Kenya, Tanzania, Turkey, Vietnam, and several countries in Southern Africa. Also, CDC continues to work with international partners, including the Stop TB Partnership,**** to strengthen TB control in countries with high TB incidence.
To address the disproportionately high rate of TB among U.S.-born blacks, CDC is working with its state and local partners to focus attention on the problem of TB in the black community. To better understand how to reduce these disparities, CDC's TB Epidemiologic Studies Consortium is conducting the National Study of Determinants of Early Diagnosis, Prevention, and Treatment of TB in the African-American Community.
HIV is the most important known risk factor for progression from latent TB infection (LTBI) to TB disease. CDC recommends routine screening for HIV for all persons with TB or LTBI at the initiation of TB or LTBI treatment.§§§§ CDC continues to work with domestic and international partners to increase awareness of TB/HIV coinfection and improve the integration of TB/HIV health-care services (8).
In February 2008, the World Health Organization released its fourth global report on anti-TB drug resistance, which indicated that the number of MDR TB cases worldwide was the highest ever reported (489,139 cases in 2006) and that XDR TB had been reported in 45 countries (4). A critical need exists for new drugs and new drug regimens to address this growing challenge. The Global Alliance for TB Drug Development, of which CDC is a member, continued to make progress in this area in 2007, with new candidate drugs moving forward in clinical trials (9,10).
The findings in this report are subject to at least two limitations. First, the analysis was based on provisional data that are subject to change. This applies to TB case counts and HIV data, both of which are incomplete at this point in the reporting cycle. Second, population denominator data are drawn from multiple U.S. Census sources and also are subject to periodic adjustment in the estimates. CDC's annual TB surveillance summary, scheduled to be published in fall 2008, will provide updated data.
Despite targeted measures to control TB, the slowing decline of TB in the United States 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 collaboration with other nations to reduce TB globally. These measures are required to reach the goal of TB elimination in the United States.
The findings in this report are based, in part, on data contributed by state and local TB-control officials.
* Population denominators for TB case rates for 1993--1999 were calculated using bridged-race 1990--1999 intercensal population estimates for 1993--1999 (available at ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/NVSS/bridgepop/documentationbridgedintercena1.doc). Population denominators for TB case rates for 2000--2007 were calculated using annual estimates of the U.S. population (available at http://www.census.gov/popest/states/NST-ann-est.html).
A U.S.-born person is 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 are classified as foreign-born. For 2007, persons with unknown origin of birth represented 1.0% (139 of 13,293) 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 races are all classified as non-Hispanic. Persons identified as Hispanic can be of any race.
¶ Rate ratios of TB rates among U.S.-born blacks versus U.S-born whites for the previous 5 years were: 7.8 in 2007, 7.5 in 2006, 7.7 in 2005, 7.7 in 2004, and 7.6 in 2003.
** Additional information available at http://www.cdc.gov/epo/dphsi/casedef/tuberculosis_current.htm.
U.S. Census annual estimates for the U.S. population (2) were used to calculate the national TB rate and the percentage change from 2006 to 2007. To obtain data on national origin, the U.S. Census Current Population Survey (4) was used to calculate the TB rate and percentage change from 2006 to 2007 for U.S.-born versus foreign-born persons. The use of these different population estimates accounts for the higher annual percentage change reported among U.S-born versus foreign-born persons compared with the annual percentage change reported for the national TB rate.
§§ Reporting of TB statistics for race/ethnicity changed beginning in 2003. A "Native Hawaiian and other Pacific Islanders" 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 because the state reports HIV data separately from TB data and 1 year later than all other states. HIV data reported by California only include the number of patients with TB that are HIV positive. The number of TB patients who tested negative for HIV, refused testing, or were not offered testing is not reported. Therefore, determining the percentage of patients with known HIV status for California is not possible. 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 done but status unknown," "unknown," and "data missing" categories.
*** Defined as a case of TB in a person with a Mycobacterium tuberculosis isolate resistant to at least isoniazid and rifampin (5).
Drug-susceptibility test results for isoniazid and rifampin were reported for 97.1% (10,633 of 10,951) and 95.7% (10,306 of 10,771) of culture-confirmed TB cases in 2005 and 2006, respectively.
§§§ Defined as a case of TB in a person with an M. tuberculosis isolate with resistance to at least isoniazid and rifampin among first-line anti-TB drugs, resistance to any fluoroquinolone (e.g., ciprofloxacin or ofloxacin), and resistance to at least one second-line injectable drug (e.g., amikacin, capreomycin, or kanamycin) (5).
¶¶¶ Additional information available at http://www.cdc.gov/ncidod/dq/pdf/comparison_1991_2007_tb_ti.pdf.
**** Additional information available at http://www.stoptb.org.
Additional information available at http://www.cdc.gov/tb/tbinafricanamericans.
§§§§ Additional information available at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5514a1.htm and http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4906a1.htm.
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Date last reviewed: 3/19/2008