Tuberculosis Morbidity -- United States, 1997

During 1997, a total of 19,855 cases of tuberculosis (TB) (7.4 cases per 100,000 population) were reported to CDC from the 50 states and the District of Columbia, representing a 7% decrease from 1996 (1) and a 26% decrease from 1992, when the number of cases peaked during the resurgence of TB in the United States. This report summarizes national TB surveillance data for 1997 and compares it with similar data for previous years. The findings indicate that, although the overall number of TB cases continued to decrease, trends in the number of reported cases and TB case rates differed by geographic area and population characteristics.

In 1997, six states (California, Florida, Illinois, New Jersey, New York, and Texas) reported 57% of all TB cases (Table_1). Since 1992, the number of cases reported from each of these states decreased substantially. Cases of TB remained concentrated in urban areas: in 1997, 40% of TB cases were reported from 64 major cities. The four largest of these cities (i.e., New York, Los Angeles, Chicago, and Houston) reported an overall decrease in total cases during 1992-1997.

During 1992-1997, the overall decrease in TB cases primarily reflected the substantial decline in cases among U.S.-born persons in all age groups (Table_2). The number of cases among foreign-born persons increased 6% during this period, reflecting a small increase among adults aged 25-44 years, a larger increase among adults aged greater than or equal to 45 years, and a substantial decline among children aged less than 15 years.

The proportion of TB cases among foreign-born persons has increased steadily since the mid-1980s (Figure_1) and increased markedly since 1992 (from 27% in 1992 to 39% in 1997). The TB case rate for foreign-born persons has remained at least four to five times higher than that for U.S.-born persons.

During 1997, the percentage of TB cases for which drug-susceptibility results for initial Mycobacterium tuberculosis isolates were reported was 84% (13,386 of 15,986 culture-positive cases). Of the 42 states that reported drug-susceptibility results for at least 75% of culture-positive cases, 963 (7.6%) isolates were resistant to at least isoniazid, and 171 (1.3%) were resistant to at least isoniazid and rifampin (i.e., multidrug-resistant TB {MDR-TB}). Of these 42 states, 27 reported at least one MDR-TB case; however, 47% of all MDR-TB cases were reported from New York (n=47) and California (n=34).

Information about the human immunodeficiency virus (HIV) status of persons with TB reported to the national surveillance system is limited. In 1997, only 3485 (50%) of 6915 TB case reports for persons aged 25-44 years included information about HIV status, and only 15 states reported HIV test results for at least 75% of cases in persons in this age group. Of these 15 states, the percentage of TB cases in persons aged 25-44 years who were coinfected with HIV ranged from zero (North Dakota and South Dakota) to 48% (Florida). Reporting of HIV status has improved slowly since 1993, the year such information was first included on TB case reports submitted to CDC. In 1993, information about HIV status was reported for 33% of TB cases in persons aged 25-44 years, and six states reported this information for at least 75% of cases among persons in this age group (2).

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

Editorial Note

Editorial Note: The findings in this report highlight several important trends in reported cases of TB in the United States. First, for the fifth consecutive year, the total number of reported cases decreased. Second, declines during 1992-1997 were sustained in states reporting the largest number of TB cases, particularly within major urban communities. Third, the overall decline in reported TB cases reflected a substantial decrease in cases among U.S.-born persons and a small increase in the number of cases among foreign-born persons.

The decline in the overall number of reported TB cases has been attributed to stronger TB-control programs that emphasize promptly identifying persons with TB, initiating appropriate therapy, and ensuring completion of therapy (3). The resulting decline in cases among U.S.-born persons probably reflected reduced community transmission of M. tuberculosis, particularly in areas with a high incidence of acquired immunodeficiency syndrome (AIDS). In comparison, the relatively stable number of cases among foreign-born persons indicated that most cases of active TB disease among foreign-born persons residing in the United States result from infection with M. tuberculosis in the person's country of birth (4).

To reduce active TB disease among foreign-born persons residing in the United States, CDC, in collaboration with state and local health departments, is developing a comprehensive plan that will include strategies to improve case finding and prevention activities. However, not all foreign-born persons have the same risk for active TB disease. For example, persons from countries with established market economies and most former socialist countries of Europe are at low risk for active TB disease and may benefit least from screening (4).

Two important factors in the resurgence of TB in the United States during the late 1980s were the HIV/AIDS epidemic and the emergence of MDR-TB. Because incomplete reporting has limited analysis of national TB surveillance data by HIV status, state health departments have compared TB and AIDS registries to help estimate the proportion of reported TB cases with HIV coinfection. In the most recent registry comparison conducted by the 50 states and Puerto Rico, 14% of all TB cases (27% of cases in persons aged 25-44 years) reported during 1993-1994 had a match in the AIDS registry (5). Both this study and recent TB surveillance data indicate that the impact of the HIV/AIDS epidemic also differs by geographic location (5,6).

HIV-infected persons are at high risk for active TB disease after infection with M. tuberculosis. Thus, reducing community transmission of M. tuberculosis by promptly identifying and treating persons who have infectious TB is an important first step in preventing further TB disease among HIV-infected persons. The next steps include promptly identifying HIV-infected contacts of persons with infectious TB and ensuring that contacts who may be infected with M. tuberculosis complete appropriate preventive therapy. Other important strategies include screening for M. tuberculosis infection among persons with recently identified HIV infection, ensuring completion of preventive therapy among those with M. tuberculosis infection, and periodic monitoring and education of those who are not infected with M. tuberculosis (7,8).

Outbreaks of MDR-TB, particularly among HIV-infected persons, contributed to the resurgence of TB in the late 1980s and early 1990s. Since CDC began monitoring anti-TB drug resistance through the national TB surveillance system in 1993, levels of isoniazid resistance have been relatively stable, and the number and proportion of MDR-TB cases has decreased (9). Nevertheless, 43 states and the District of Columbia reported at least one MDR-TB case during 1993-1997. All health departments should be prepared to promptly identify persons who have active TB disease, to ensure that standards of care are met with respect to diagnosis and treatment (including prompt initiation and completion of therapy), and to identify and appropriately treat those who may have been infected through close contact with persons who have infectious TB.

References

1. CDC. Tuberculosis morbidity -- United States, 1996. MMWR 1997;46:695-700.

2. CDC. Reported tuberculosis in the United States, 1993. Atlanta: US Department of Health and Human Services, CDC, 1994.

3. McKenna MT, McCray E, Jones JL, Onorato IM, Castro KG. The fall after the rise: tuberculosis in the United States, 1991 to 1994. Am J Public Health (in press).

4. 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.

5. Moore M, McCray E, Onorato IM. The proportion of U.S. TB cases with a match in the AIDS registry {Abstract}. Am J Respir Crit Care Med 1997;155:23.

6. CDC. Reported tuberculosis in the United States, 1996. Atlanta: US Department of Health and Human Services, CDC, 1997.

7. CDC. 1997 USPHS/IDSA guidelines for the prevention of opportunistic infections in persons infected with human immunodeficiency virus. MMWR 1997;46(no. RR-12):10-12.

8. CDC. Anergy skin testing and preventive therapy for HIV-infected persons: revised recommendations. MMWR 1997;46(no. RR-15).

9. Moore M, Onorato IM, McCray E, Castro KG. Trends in drug-resistant tuberculosis in the United States, 1993-1996. JAMA 1997;278:833-7.

TABLE 1. Number of reported tuberculosis cases, percentage change in number of cases, and
case rates,* by state and year -- United States, 1992 and 1997
==============================================================================================
                             No. cases                                    Case rate
                        --------------------                           -------------------
                          1992         1997     % Change from 1992      1992      1997
State                                                 to 1997
----------------------------------------------------------------------------------------------
Alabama                    418          405             - 3%             10.1       9.4
Alaska                      57           78              37%              9.7      12.8
Arizona                    259          296              14%              6.8       6.5
Arkansas                   257          200             -22%             10.7       7.9
California               5,382        4,059             -25%             17.4      12.6
Colorado                   104           94             -10%              3.0       2.4
Connecticut                156          128             -18%              4.8       3.9
Delaware                    55           39             -29%              8.0       5.3
District of Columbia       146          110             -25%             24.8      20.8
Florida                  1,707        1,400             -18%             12.7       9.6
Georgia                    893          696             -22%             13.2       9.3
Hawaii                     273          167             -39%             23.5      14.1
Idaho                       26           15             -42%              2.4       1.2
Illinois                 1,270          974             -23%             10.9       8.2
Indiana                    247          168             -32%              4.4       2.9
Iowa                        49           74              51%              1.7       2.6
Kansas                      56           78              39%              2.2       3.0
Kentucky                   402          199             -50%             10.7       5.1
Louisiana                  373          406               9%              8.7       9.3
Maine                       24           21             -13%              1.9       1.7
Maryland                   442          340             -23%              9.0       6.7
Massachusetts              428          268             -37%              7.1       4.4
Michigan                   495          374             -24%              5.2       3.8
Minnesota                  165          161             - 2%              3.7       3.4
Mississippi                281          245             -13%             10.7       9.0
Missouri                   245          248               1%              4.7       4.6
Montana                     16           18              13%              1.9       2.0
Nebraska                    28           22             -21%              1.7       1.3
Nevada                      99          112              13%              7.5       6.7
New Hampshire               18           17             - 6%              1.6       1.4
New Jersey                 984          718             -27%             12.6       8.9
New Mexico                  88           71             -19%              5.6       4.1
New York                 4,574        2,265             -50%             25.2      12.5
North Carolina             604          463             -23%              8.8       6.2
North Dakota                11           12               9%              1.7       1.9
Ohio                       358          286             -20%              3.2       2.6
Oklahoma                   216          212             - 2%              6.7       6.4
Oregon                     145          161              11%              4.9       5.0
Pennsylvania               758          528             -30%              6.3       4.4
Rhode Island                54           38             -30%              5.4       3.9
South Carolina             387          328             -15%             10.7       8.7
South Dakota                32           19             -41%              4.5       2.6
Tennessee                  527          467             -11%             10.5       8.7
Texas                    2,510        1,992             -21%             14.2      10.2
Utah                        78           36             -54%              4.3       1.7
Vermont                      7            6             -14%              1.2       1.0
Virginia                   457          350             -23%              7.2       5.2
Washington                 306          305                0              6.0       5.4
West Virginia               92           54             -41%              5.1       3.0
Wisconsin                  106          130              23%              2.1       2.5
Wyoming                      8            2             -75%              1.7       0.4

Total                    26,673      19,855             -26%             10.5       7.4
----------------------------------------------------------------------------------------------
* Per 100,000 population.
==============================================================================================

TABLE 2. Number of persons with reported cases of tuberculosis and percentage change in number of cases, by country of birth,
age group, and year -- United States, 1992 and 1997
===================================================================================================================================
                                                                            Country of birth
                                   ------------------------------------------------------------------------------------------------
                                                   United States                                         Other
                                   -----------------------------------------------       ------------------------------------------
                                      No. reported cases                                  No. reported cases
                                   ------------------------                              -------------------
                                      1992            1997     % Change from 1992         1992          1997    % Change from 1992
Age group (yrs)                                                     to 1997                                          to 1997
-----------------------------------------------------------------------------------------------------------------------------------
   0-14                               1,285            961            -25%                  411          291           -29%
  15-24                                 908            565            -38%                1,047        1,094             4%
  25-44                               7,363          3,753            -49%                3,007        3,070             2%
  45-64                               4,888          3,376            -31%                1,557        1,851            19%
   >=65                               4,750          3,198            -33%                1,244        1,429            15%

  Total*                             19,194         11,853            -38%                7,266        7,735             6%
-----------------------------------------------------------------------------------------------------------------------------------
* Persons for whom age was not stated were excluded (seven in 1997, 35 in 1992)
===================================================================================================================================

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