Impact of immigration on the molecular epidemiology of tuberculosis in Rhode Island

Abstract

While foreign-born persons constitute only 11% of the population in the state of Rhode Island, they account for more than 65% of incident tuberculosis (TB) annually. We investigated the molecular-epidemiological differences between foreign-born and U.S.-born TB patients to estimate the degree of recent transmission and identify predictors of clustering. A total of 288 isolates collected from culture-confirmed TB cases in Rhode Island between 1995 and 2004 were fingerprinted by spoligotyping and 12-locus mycobacterial interspersed repetitive units. Of the 288 fingerprinted isolates, 109 (37.8%) belonged to 36 genetic clusters. Our findings demonstrate that U.S.-born patients, Hispanics, Asian/Pacific islanders, and uninsured patients were significantly more likely to be clustered. Recent transmission among the foreign-born population was restricted and occurred mostly locally, within populations originating from the same region. Nevertheless, TB transmission between the foreign-born and U.S.-born population should not be neglected, since 80% of the mixed clusters of foreign- and U.S.-born persons arose from a foreign-born source case. We conclude that timely access to routine screening and treatment for latent TB infection for immigrants is vital for disease elimination in Rhode Island.

Fig. 1.

(A) Number and proportion of all reported TB cases in Rhode Island by country of birth, 1995 to 2004. (B) Number and proportion of new isolated genotypes in TB cases in Rhode Island by country of birth, 1996 to 2004. (C) Distribution of major M. tuberculosis lineages according to patient region of origin: comparison between all unique strains isolated in TB patients of Rhode Island (RI) between January 1995 and December 2004, and all strains included in the international genotyping database (SITVIT 2). (The world outline map used in the figure was obtained from WorldAtlas.com and is used with permission.).