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Trends in Tuberculosis Morbidity --- United States, 1992--2002

During 2002, a total of 15,078 TB cases were reported to CDC, representing a 5.7% decline from 2001, a 43.5% decline from the 1992 peak of the TB resurgence, and the lowest recorded TB rate in the United States since reporting began in 1953. Declines have occurred since 1992 in all age groups, racial/ethnic populations, and regions of the United States. Despite this progress, the 2002 rate of 5.2 per 100,000 population remained higher than the 2000 interim goal of 3.5 set as part of the national strategic plan for TB elimination (<1 case per 1,000,000 by 2010) (1). This report summarizes data from the national TB surveillance system for 2002 and describes trends over the past decade. Overall national declines in TB incidence mask substantial disparities between rates in the majority of U.S. residents and rates in the two populations, foreign-born persons and U.S.-born non-Hispanic blacks, which now account for approximately three fourths of TB cases. Further progress toward TB elimination in the United States will depend on 1) domestic programs that provide services to foreign-born persons with latent TB infection, 2) collaborative efforts that reduce the burden of TB disease globally, and 3) intensified TB-control efforts that address higher TB rates in the U.S.-born non-Hispanic black population.

The 50 states and the District of Columbia report to the national TB surveillance system by using a standard case definition and report form (2). Completeness of reporting to the national system is estimated to be >95% (3). Data were analyzed for cases reported during 1992--2002 by using case reports updated as of February 18, 2003. 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; others were classified as foreign-born. U.S.-born and foreign-born population counts in 1992 were obtained from postcensus estimates (4). Overall U.S.-born and foreign-born population counts for 2002 were based on an extrapolation from the April 2000 U.S. Census, and the distribution of racial/ethnic groups was estimated from the March 2000 Current Population Survey (5).

In 2002, the overall TB case rate of 5.2 represents a decline of 7.1% from 2001 and 50.5% from 1992. During 1992--2002, case rates declined in all but three states (Table 1). Five states (California, Florida, Illinois, New York, and Texas) accounted for 52.5% of cases and 68.3% of the overall decrease in the number of cases; case rates in these states declined an average of approximately 50% during 1992--2002. The proportion of patients with multidrug-resistant TB (i.e., resistance to at least isoniazid and rifampin) decreased from 486 (2.7%) of 17,690 culture-positive cases with initial susceptibility results in 1993 (the first year for which data were collected) to 138 (1.3%) of 10,601 cases in 2002.

During 1992--2002, rates declined in both the U.S.-born and the foreign-born populations. However, the decline was substantially less among foreign-born populations (Table 2), and the ratio of foreign-born to U.S.-born rates doubled, from 4.2 in 1992 to 8.4 in 2002. In 2002, for the first time, TB cases among foreign-born persons accounted for the majority (51.0%) of TB cases in the United States. The number of states with >50% of cases among foreign-born persons increased from four in 1992 to 22 in 2002 (Figure). In seven states, approximately 70% of cases were among foreign-born persons (New Hampshire [79.0%], Idaho [76.9%], Minnesota [76.4%], California [75.8%], Massachusetts [75.7%], Hawaii [74.3%], and Colorado [70.2%]. As in 1992, the most common birth countries for foreign-born persons with TB in 2002 were Mexico (24.8%), the Philippines (11.3%), Vietnam (8.6%), India (7.6%), China (4.5%), Haiti (3.4%), and South Korea (2.7%). The proportion of patients who completed recommended treatment within 1 year was 81.0% in the U.S.-born and 79.2% in the foreign-born populations in 1999 (the most recent year for which these outcome data were available).

Despite a 68.4% decline in rates from 1992, U.S.-born non-Hispanic blacks in 2002 continued to have the highest TB rate of any U.S.-born racial/ethnic population. U.S.-born non-Hispanic blacks comprised the largest number of TB cases among both U.S.-born and foreign-born populations, representing 46.7% of TB cases in U.S.-born persons and approximately one fourth of all cases. Among U.S.-born racial/ethnic populations, rates among non-Hispanic blacks were 7.5 times higher and 2.1 times higher, respectively, than those among non-Hispanic whites and Hispanics, the two other U.S.-born groups that account for the majority of TB cases (Table 2).

Reported by: Div of Tuberculosis Elimination, National Center for HIV, STD, and TB Prevention, CDC.

Editorial Note:

Since 1992, when TB cases in the United States peaked after 7 years of stable or increasing rates, TB case rates have declined an average of 5% per year. The strengthened TB control efforts that have been effective in reversing increases in TB rates among U.S.-born persons have had far less effect on TB rates among foreign-born persons (6). The reasons for these differences are unclear and require further study. The differences are not related to timeliness of completion of therapy, which is similar among U.S.-born and foreign-born persons. However, the accelerated decline in overall U.S. TB cases probably resulted from the implementation of control measures that reduced ongoing transmission of Mycobacterium tuberculosis and the subsequent number of TB cases caused by recent infection (7). These measures are relatively less effective in controlling TB among foreign-born persons. Genotyping studies of M. tuberculosis isolates suggest that the majority of TB cases in foreign-born persons are the result of progression to disease among persons infected before immigrating to the United States (8).

Closing the gap in TB rates between U.S.-born and foreign-born populations is critical to TB elimination in the United States. Success will depend on domestic programs that provide services to foreign-born persons with latent TB infection and on collaborative efforts that reduce the burden of TB disease globally. To address the high rates in the foreign-born population, CDC is collaborating with other national and international public health organizations to 1) optimize overseas screening of immigrants and refugees, 2) enhance the notification system that alerts local health departments to the arrival of immigrants or refugees with suspected TB to improve diagnosis and treatment, 3) establish a binational TB referral and case management system for the United States and Mexico to improve treatment completion by TB patients who cross the United States--Mexico border (the U.S.--Mexico Binational TB Referral and Case Management Project), 4) identify and treat persons arriving from high-incidence countries who have latent TB infection, and 5) strengthen collaborations with the World Health Organization and other international partners aimed at improving TB control in high-incidence countries (the STOP TB Partnership). In support of these efforts, CDC and its 22 partner research institutes, clinical centers, and health departments in the United States and Canada that compose the Tuberculosis Epidemiologic Studies Consortium have initiated a study to identify missed opportunities for TB prevention among foreign-born persons.

Although intensified TB control efforts helped reduce the TB case rate in the U.S.-born non-Hispanic black population by approximately 70% during 1992--2002, that rate has remained approximately eight times higher than the rate among non-Hispanic whites. Because much of this disparity is associated with socioeconomic status (9), intensified outreach programs tailored to the needs of low-income persons might accelerate TB elimination. CDC is funding demonstration projects in South Carolina, Georgia, and Chicago, Illinois, to identify innovative strategies to improve TB screening, diagnosis, and treatment adherence in high-risk black communities.

Elimination of health disparities is one of the national health goals for 2010 (Goal 2) (10). Closing the gaps in TB rates will help achieve this and the goal of TB elimination.

References

  1. CDC. A strategic plan for the elimination of tuberculosis in the United States. In: CDC Surveillance Summaries (April 21). MMWR 1989;38(No. S-3).
  2. CDC. Reported tuberculosis in the United States, 2001. Atlanta, Georgia: U.S. Department of Health and Human Services, CDC, September 2002. Available at http://www.cdc.gov/nchstp/tb/surv/surv.lhtm.
  3. Curtis AB, McCray E, McKenna M, Onorato IM. Completeness and timeliness of tuberculosis case reporting. Am J Prev Med 2001;20:108--12.
  4. U.S. Census Bureau. Native and foreign-born resident population estimates of the United States by age and sex: April 1, 1990 to July 1, 1999. Available at http://eire.census.gov/popest/archives/national/us_nativity/nbtab003.txt and fbtab003.txt.
  5. U.S. Census Bureau. Profile of the foreign-born population in the United States: 2000. Available at http://www.census.gov/prod/2002pubs/p23-206.pdf.
  6. McKenna MT, McCray E, Jones JL, Onorato M, Castro KG. The fall after the rise: tuberculosis in the United States, 1991 through 1994. Am J Public Health 1998;88:1059--63.
  7. Talbot EA, Moore M, McCray E, Binkin NJ. Tuberculosis among foreign-born persons in the United States, 1993--1998. JAMA 2000;284:2894--900.
  8. Zuber PLF, McKenna MT, Binkin NJ, Onorato IM, Castro KG. Long-term risk of tuberculosis among foreign-born persons in the United States. JAMA 1997;278:304--7.
  9. Cantwell MF, McKenna MT, McCray E, Onorato IM. Tuberculosis and race/ethnicity in the United States: impact of socioeconomic status. Am J Respir Crit Care Med 1997;157:1016--20.
  10. U.S. Department of Health and Human Services. Healthy people 2010 (2nd ed., 2 vols.). Washington, DC: U.S. Government Printing Office, November 2000.


Table 1

Table 1
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Table 2

Table 2
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Figure

Figure 3
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