Tuberculosis Among Foreign-Born Persons Who Had Recently Arrived in the United States -- Hawaii, 1992-1993, and Los Angeles County, 1993

During 1986-1994, the number of tuberculosis (TB) cases reported annually among foreign-born persons in the United States increased 55% (from 4925 to 7627), and the proportion of all cases accounted for by persons who were foreign-born increased from 22% to 32% -- increases that reflect, in part, effects of recent immigration (1). The largest numbers of foreign-born persons with TB originated from Mexico, Philippines, and Vietnam; persons from these countries currently account for the largest numbers of recent immigrants to the United States (2). This report summarizes a review of foreign-born persons in whom TB was diagnosed in Hawaii during 1992-1993 and in Los Angeles County during 1993 and assesses the impact of screening on the identification of TB among foreign-born persons residing in the United States for less than or equal to 1 year at the time of diagnosis.

Immigrants and refugees are the only groups of foreign-born persons required to undergo screening for TB before obtaining a visa to enter the United States. The screening consists of a chest radiograph for persons aged greater than or equal to 15 years. If the radiograph is compatible with active TB, sputum smear examinations are conducted on 3 consecutive days to detect acid-fast bacilli (AFB). Based on these results, applicants with findings compatible with current or past TB infection are classified as class A, TB infectious; class B1, TB clinically active; class B2, TB not clinically active; or class B3, TB old or healed (Table_1). Persons with a class A status are required to undergo anti-TB therapy until they are AFB-smear-negative before being allowed to apply for a waiver to enter the country; no travel restrictions are placed on persons with a class B status.

Information about the classification of immigrants and refugees is sent by the Immigration and Naturalization Service (INS) to CDC, which notifies the state or local health departments of the arrival of each person with an A, B1, or B2 status, and informs the immigrants and refugees that they should report promptly to their health department. Since the introduction of new guidelines for the medical examination of immigrants and refugees in 1991 (3), the contribution of the examination process to the identification of TB among recently arrived foreign-born persons has not been evaluated. Hawaii and Los Angeles County were selected for this analysis because most of their reported TB cases are among foreign-born persons.

TB registries in Hawaii (1990 population: 1,104,668) and Los Angeles County (1990 population: 8,292,057) were examined to identify all foreign-born persons in whom TB had been diagnosed within 1 year of arrival through comparison of the dates of diagnosis and arrival in the United States. Case records were matched against CDC's Tracking System of Immigrants and Refugees with Suspected TB database to determine both the percentage of foreign-born persons with TB that had been identified as B1 and B2 before arrival in the United States and the percentage of those classified as B1 and B2 in whom active TB was diagnosed after arrival.

In Hawaii during 1992-1993, a total of 429 (82%) TB cases were diagnosed in foreign-born persons, of whom 261 (61%) had resided in the United States for less than or equal to 1 year (Table_2). Most of these cases (211 {81%}) were in persons from Philippines, including 101 who were World War II veterans who entered the United States under a temporary provision of the Immigration Act of 1990, which exempted them from medical examination while applying for U.S. citizenship during 1992-1995. Based on inclusion of these veterans, 78 (30%) TB cases in foreign-born persons were classified as B1, and 17 (7%) as B2; the screening process did not identify 166 (64%) cases. Based on the exclusion of these veterans, 78 (49%) of the remaining 160 cases were classified as B1 and 17 (11%) as B2; the screening process did not identify 65 (41%) cases (Table_3).

In Los Angeles County during 1993, a total of 1228 (64%) TB cases were diagnosed among foreign-born persons, of whom 261 (21%) had resided in the United States less than or equal to 1 year. Of these, 79 (30%) originated from Mexico, 71 (27%) from Philippines, 36 (14%) from Vietnam, and 48 (18%) from other countries in Asia (Table_2). Sixty-four (25%) persons previously had been classified as B1 and 30 (11%) as B2; the screening process did not identify 167 (64%) cases. Most of the cases from Philippines and Vietnam (65% and 58%, respectively) had been identified through screening before emigration; in comparison, 3% of cases from Mexico and other countries in Central America had been identified by previous screening (Table_3). The number of World War II veterans included in the Los Angeles County cases could not be determined; however, no more than 13 persons with TB could meet the criteria for inclusion in the category based on nationality, age, and year of arrival in the United States.

The prevalence of confirmed TB within 1 year after arrival in the United States among persons classified abroad as B1 was 14% in Hawaii and 11% in Los Angeles County, and among those classified as B2, 2% and 3%, respectively.

Reported: AC Ignacio, MD, Tuberculosis/Hansen's Disease Br; RL Vogt, MD, State Epidemiologist, Hawaii Dept of Health. LS Knowles, MPH, PT Davidson, MD, Tuberculosis Control, Los Angeles County Dept of Health Svcs, Los Angeles. Div of Quarantine, National Center for Infectious Diseases; Div of Field Epidemiology, Epidemiology Program Office; Div of Tuberculosis Elimination, National Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The findings in this report document two important differences in the epidemiology of TB among recently arrived foreign-born persons in Hawaii and Los Angeles County. First, in Hawaii, 61% of foreign-born persons in whom TB was diagnosed had resided in the United States for less than or equal to 1 year, compared with 21% in Los Angeles County. Second, although the proportion of persons in whom TB was diagnosed shortly after arrival and who had not been detected through screening was similar in both areas, the characteristics of these groups were different. In Hawaii, approximately 60% of the previously undetected cases occurred in World War II veterans from Philippines who were exempted from medical examination (4). In comparison, in Los Angeles County, approximately half of the undetected cases occurred among persons from Mexico and Central America, whose immigration status could not be determined during this investigation. These differences underscore the need for TB-control programs to conduct reviews of the epidemiology of TB among foreign-born persons to enable improved case detection and prevention efforts.

The findings in this report also underscore the importance of mandatory screening in the timely diagnosis and treatment of TB among those persons who emigrated to the United States from Philippines and Vietnam. Most persons who had emigrated from these two countries and who had TB diagnosed within 1 year of arrival had been identified previously through the mandatory immigrant and refugee screening system; among persons who were not identified, some may have developed TB after entering the country. In contrast, the system contributed only minimally to the early identification of TB among persons from Mexico and Central America. Potential explanations for the relative ineffectiveness of mandatory screening among these persons include 1) a lower screening sensitivity in these countries to detect active TB, 2) inadequate or incomplete dissemination of information from the ports of entry most commonly used by these populations, and 3) a higher proportion of persons from Mexico and Central America who entered the United States under visa categories not requiring medical examination or who entered illegally. In Hawaii, where it was possible to assess immigration status for new arrivals, less than 10% of the cases diagnosed within the first year were among persons in other visa categories or who were in the United States illegally; similar assessments could not be performed in Los Angeles County.

The findings in this report also document the high prevalence of active TB among persons classified as B1 and B2. In addition to confirmed TB, a high proportion of those classified as B1 and B2 have abnormal chest radiographs and positive skin tests and may benefit from preventive chemotherapy (5). These persons should receive prompt and active follow-up after their arrival in the United States.

An important strategy for preventing and treating TB among foreign-born persons is ensuring that most persons who intend to become residents of the United States and have active TB are detected before entering the country. The findings in this report suggest the need for some improvements in the screening process abroad and some operational modifications. CDC, in collaboration with state and local health departments, is evaluating the different stages of the screening and tracking process to make recommendations for future strategies. The evaluation includes assessments -- similar to those in Hawaii and Los Angeles County -- in other areas reporting large proportions of their TB cases among foreign-born persons, a review of data transmission from ports of entry, and a reevaluation of the current screening criteria and supervision at screening sites.

References

1. McKenna MT, McCray E, Onorato I. The epidemiology of tuberculosis among foreign-born persons in the United States, 1986 to 1993. N Engl J Med 1995;332:1071-6.

2. Immigration and Naturalization Service. Statistical yearbook of the Immigration and Naturalization Service, 1993. Washington, DC: Immigration and Naturalization Service, 1994.

3. CDC. Technical instruction for medical examination of aliens. Atlanta: US Department of Health and Human Services, Public Health Service, 1991.

4. CDC. Tuberculosis in Philippine national World War II veterans immigrating to Hawaii, 1992-1993. MMWR 1993;42:656-7,663.

5. Bass JB Jr, Farer LS, Hopewell PC, et al. Treatment of tuberculosis and tuberculosis infection in adults and children. Am J Respir Crit Care Med 1994;149:1359-74.

TABLE 1. Classification for tuberculosis (TB) screening abroad of immigrants and
refugees to the United States
=================================================================================================
Chest radiograph           Sputum smear         Classification
------------------------------------------------------------------------------
Abnormal, suggestive of    Positive for         TB infectious (A)
 active pulmonary TB        acid-fast bacilli

Abnormal, suggestive of    Negative for acid-   TB, clinically active, not
 active pulmonary TB        fast bacilli         infectious (B1*)

Abnormal, suggestive of    Not required         TB, not clinically active (B2)
 pulmonary TB, not
 clinically active

Abnormal, only because     Not required         Consistent with TB, old or
 of a calcified hilar                            healed (B3)
 lymph node, a calci-
 fied primary complex,
 or a calcified granuloma

Abnormal, not              Not required         Other chest condition (B)
 consistent with TB

Normal                     Not required         Normal
------------------------------------------------------------------------------
* Persons with radiographic or other evidence of extrapulmonary TB, clinically active, also are
  classified as B1.
=================================================================================================

TABLE 2. Number and percentage of tuberculosis cases diagnosed among
foreign-born persons who had resided in the United States <=1 year, by area of origin
-- Hawaii, 1992-1993, and Los Angeles County, 1993
=======================================================================================
                        Hawaii (n=261)        Los Angeles (n=261)
                       ----------------       -------------------
Area of origin          No.        (%)           No.       (%)
-----------------------------------------------------------------
Asia
  Philippines          211       (80.8)          71      (27.2)
  Vietnam               16       ( 6.1)          36      (13.8)
  Other Asian           27       (10.3)          48      (18.4)

Mexico and
 Central America
  Mexico                 1       ( 0.4)          79      (30.3)
  Central Amerca         0                        9      ( 3.4)

Other                    6       ( 2.3)          18      ( 6.9)
-----------------------------------------------------------------
=======================================================================================

TABLE 3. Number and percentage of tuberculosis (TB) cases among foreign-born
persons who had resided in the United States <=1 year, by country or geographic area
of origin and screening category* -- Hawaii, 1992-1993, and Los Angeles County, 1993
=================================================================================================
                                    Hawaii                          Los Angeles County
                       --------------------------------       -------------------------------
                          B1          B2       Other             B1          B2       Other
                       --------    --------  ----------       --------    --------  ---------
Area of origin         No.   %     No.   %    No.   %         No.   %     No.  %     No.  %
---------------------------------------------------------------------------------------------
Philippines                                                   44  (48)    12  (17)   25  (35)
 Nonveterans           69  (63)    10  ( 9)   31  ( 28)
 World War II
  veterans                                   101  (100)

Vietnam                 7  (44)     1  ( 6)    8  ( 50)       20   (55)    1  ( 3)   15  (42)

Other Asian countries   2  ( 7)     6  (22)   19  ( 70)        7   (15)   14  (29)   27  (56)

Mexico and Central      0           0          1  (100)        2   ( 2)    1  ( 1)   85  (97)
 America

All other countries     0           0          6  (100)        1   ( 6)    2  (11)   15  (83)

Total                  78  (30)    17  ( 7)  166  ( 64)       64   (25)   30  (11)  167  (64)

Total excluding        78  (49)    17  (11)   65  ( 41)       64   (25)   30  (11)  167  (64)
 WWII veterans
---------------------------------------------------------------------------------------------
* B1=an immigrant or refugee with clinically active TB but sputum-smear-negative for acid-fast
  bacilli; B2=an immigrant or refugee with nonclinically active TB; Other=any foreign-born person
  in whom TB was diagnosed that was not classified as B1 or B2.
=================================================================================================

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