The Foreignness of Germs: The Persistent Association of Immigrants and Disease in American Society

Over the past decade, there has been a reduction in the incidence of tuberculosis in New York City and in the United States. However, the reduction has been confined mainly to U.S.-born persons. Understanding the reasons for the lack of reduction among non-U.S.-born persons may lead to new strategies for tuberculosis control. We performed DNA fingerprinting with the IS6110 insertion sequence of the organisms isolated from patients with culture-positive tuberculosis in northern Manhattan from 1990 to 1999. The goal was to identify the strains responsible for multiple infections, presumably through recent transmission (clusters of cases), as well as the strains found in only one patient, presumably representing reactivation of latent infection. Of 546 available isolates of Mycobacterium tuberculosis, 261 (48 percent) belonged to a cluster and 285 (52 percent) did not. In multivariate analysis, significant predictors of noncluster status included birth outside the United States (odds ratio for a strain causing a cluster among non-Hispanic foreign-born patients, 0.31; 95 percent confidence interval, 0.14 to 0.66; odds ratio among Hispanic foreign-born patients, 0.51; 95 percent confidence interval, 0.30 to 0.88), age greater than 60 years (odds ratio, 0.37), and diagnosis after 1993 (odds ratio, 0.50). All these characteristics appeared to be associated with reactivation disease rather than with tuberculosis due to recent transmission. Homelessness was associated with clustering (odds ratio, 1.78; 95 percent confidence interval, 0.99 to 3.20) and therefore with recent transmission. These findings from northern Manhattan suggest that among foreign-born persons, tuberculosis is largely caused by reactivation of latent infection, whereas among U.S.-born persons, many cases result from recent transmission. Strategies for the control and elimination of tuberculosis among foreign-born persons at high risk should be directed toward the treatment of latent tuberculosis infection.

One third of the world's population is infected with Mycobacterium tuberculosis, and in the developed countries immigration is a major force that sustains the incidence of tuberculosis. We studied the effects of immigration on the epidemiology of tuberculosis and its recent resurgence in the United States. We analyzed data from the national tuberculosis reporting system of the Centers for Disease Control and Prevention. Since 1986 reports of tuberculosis have included the patient's country of origin. Population estimates for foreign-born persons were derived from special samples from the 1980 and 1990 censuses. The proportion of persons reported to have tuberculosis who were foreign-born increased from 21.6 percent (4925 cases) in 1986 to 29.6 percent (7346 cases) in 1993. For the entire eight-year period, most foreign-born patients with tuberculosis were from Latin America (43.9 percent; 21,115 cases) and Southeast Asia (34.6 percent; 16,643 cases). Among foreign-born persons the incidence rate was almost quadruple the rate for native residents of the United States (30.6 vs. 8.1 per 100,000 person-years), and 55 percent of immigrants with tuberculosis had the condition diagnosed in their first five years in the United States. Immigration has had an increasingly important effect on the epidemiology of tuberculosis in the United States. It will be difficult to eliminate tuberculosis without better efforts to prevent and control it among immigrants and greater efforts to control it in the countries from which they come.