Prevalence of Tuberculous Infection Among U.S. Residents of Cuban Descent -- Dade County, Florida, 1982-84

The strategic plan to eliminate tuberculosis (TB) in the United States emphasizes the need for improved understanding of the epidemiology of tuberculous infection among recent immigrants and other groups at increased risk for TB (1). Data regarding the prevalence of tuberculous infection are limited for groups such as U.S. residents of Cuban descent (i.e., Cubans) and other minority populations. To estimate the prevalence of tuberculous infection among self-reported Cubans, CDC's National Center for Health Statistics analyzed data from tuberculin skin testing performed on all examinees aged 6 months to 74 years in Dade County (which includes incorporated Miami), Florida (1990 population: 1.9 million; Hispanic population: 950,000), during the first Hispanic Health and Nutrition Examination Survey (HHANES), 1982-84 * (2).

As part of HHANES, each person examined was tested with an intradermal injection of 5 tuberculin units of purified protein derivative. The presence of induration was assessed by a nurse 48-72 hours later; induration of greater than or equal to 10 mm was considered a positive test. Because HHANES employed a complex survey design, sampling weights were used to estimate the prevalence of tuberculous infection; variances of tuberculous infection rates were estimated by multiplying the variance estimates by an average design effect (2). The prevalence of tuberculous infection was age-adjusted to the 1980 U.S. census population. Because prior vaccination with bacille Calmette-Guerin (BCG) vaccine complicates interpretation of tuberculin skin tests, persons with a scar suggesting prior BCG vaccination were excluded from the analysis. Ethnicity and country of birth were self-reported by participants.

Of the 901 persons of Cuban descent who were skin tested, induration was assessed in 870 (97%); 458 (53%) were female. The mean age for the 870 persons was 37 years. The overall age-adjusted prevalence of tuberculous infection was 9.7% for males and 4.9% for females (p less than 0.05). For males, the prevalence rate increased directly with age, from 4.5% (95% confidence interval (CI)=1.1%-7.9%) for those aged 1-19 years to 14% (95% CI=8.6%-19.5%) for those aged 45-74 years (Figure 1). All females aged 1-19 years were skin-test negative; the prevalence rate was stable for females aged 20-44 years and 45-74 years (7.6% (95% CI=2.1%-13.1%) and 7.8% (95% CI=3.9%-11.6%), respectively) (Figure 1).

Of the 870 persons, 691 (79%) were born in Cuba; 160 (18%), in the United States; and 19 (2%), in other countries. The age-adjusted prevalence rate of tuberculous infection for persons born in Cuba (9.7%) was greater than for those born in the United States (1.3%). This pattern also characterized specific age groups: 5.9% and 10.3%, respectively, for persons less than or equal to 19 and 20-74 years of age who were born in Cuba, compared with 0.7% and 6.7%, respectively, for persons born in the United States.

The prevalence rate of tuberculous infection for Cubans who were smokers ** (12.0%) was almost twice that for nonsmokers (7.1%) and varied by sex: for males, 14.4% for current smokers versus 8.9% for nonsmokers; for females, 13.6% for current smokers versus 6.1% for nonsmokers.

Reported by: Medical Statistics Br, Div of Health Examination Statistics, National Center for Health Statistics, CDC.

Editorial Note

Editorial Note: Based on the 1990 U.S. census estimates of the population of Cubans in the United States (3) and the TB prevalence data collected in the 1982-84 HHANES, approximately 76,000 Cubans in the United States could be infected with TB. This estimate is consistent with other reports regarding the occurrence of TB in Hispanics in the United States. For example, in 1980, of 88,971 Cuban refugees who received chest radiographs as part of a health screening examination, 0.5% had active or suspected active TB, and 1.4% had suspected inactive TB (4). In 1990, the TB case rate for all Hispanics in the United States was 21.4 per 100,000, five times the rate of 4.2 per 100,000 for non-Hispanic whites (CDC, unpublished data).

In this study, the prevalence rates of tuberculous infection for Cubans were higher for males, persons born in Cuba, and persons who smoked. In general, males are at higher risk for tuberculous infection because of environmental factors (e.g., working with others who are infected with TB, living in crowded conditions) (5). In 1982, the incidence of TB in Cuba was 8.1 per 100,000 population (World Health Organization, unpublished data). Although cigarette smoking has been associated with TB (6,7), it is unclear whether smoking may increase the risk for tuberculous infection or may increase the likelihood of clinical TB after infection.

To help meet the national goal to eliminate TB (a case rate of less than 1 per million population by the year 2010, with an interim target of a case rate of 3.5 per 100,000 population by the year 2000 (8)), culturally appropriate strategies must be developed to prevent and control TB among Hispanics in the United States and other groups at increased risk for TB. Such strategies should emphasize 1) early identification and appropriate treatment of active cases and 2) systematic screening for tuberculous infection and preventive therapy among Hispanics in the United States at high risk for TB.

References

1. CDC. A strategic plan for the elimination of tuberculosis in the United States. MMWR 1989;38(no. S-3).

2. NCHS. Plan and operation of the Hispanic Health and Nutrition Examination Survey, 1982-84. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1985:56-61.

3. Bureau of the Census. Census Bureau releases 1990 census counts on specific racial groups (press release no. CB91-215). Washington, DC: US Department of Commerce, Bureau of the Census, June 12, 1991.

4. CDC. Follow-up on the health status of the Cuban refugees. MMWR 1980;29:343-4.

5. Hinman AR, Judd JM, Kolnick JT, Daitch PB. Changing risks in TB. Am J Epidemiol 1976;103:487-97.

6. Brown KE, Campbell AH. Tobacco, alcohol, and tuberculosis. Brit J Dis Chest 1961;55:150-8.

7. Yu GP, Hsieh CC, Peng J. Risk factors associated with the prevalence of pulmonary tuberculosis among sanitary workers in Shanghai. Tubercle 1988;69:105-12.

8. CDC. Update: tuberculosis elimination--United States. MMWR 1990;39:153-6.

• The most recent period for which data are available.

** Defined as persons who had smoked at least 100 cigarettes in their lifetimes.

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