Disparities in Tuberculosis Burden Among South Asians Living in New York City, 2001-2010

BACKGROUND: Although the number of tuberculosis (TB) cases in New York City (NYC) has declined steadily since 1993, TB control efforts have mainly benefited the United States (U.S.)-born population. In 2010, 81% of NYC TB cases were foreign-born. Six percent of foreign-born NYC residents originated from South Asia; however, this group represented 13% of incident foreign-born TB cases. We compared South Asian and other foreign-born TB cases living in NYC to explore the disproportionate burden of TB in this population.

METHODS: The study population included all foreign-born TB cases in NYC from 2001 to 2010. Tibetan cases were excluded because they originate from multiple countries, some of which are outside South Asia. Incidence by country of birth was estimated using denominators from the U.S. Census Bureau. Demographic and clinical characteristics of South Asian and other foreign-born cases were compared using crude odds ratios and 95% confidence intervals. Genotype clusters were defined as two or more NYC cases with the same genotype based on IS6110-based restriction length polymorphism and spacer oligonucleotide typing. Genotyping results were reviewed to assess clustering and recent transmission.

RESULTS: Between 2001 and 2010, 795 South Asian-born TB cases were counted in NYC. Although South Asian incidence rates declined over the study period, they were double other foreign-born rates in every year. South Asian cases were more likely than other foreign-born cases to be diagnosed within 5 years of arriving in the U.S. (52% vs. 38%, p<0.0001). The odds of HIV infection, homelessness, incarceration, and substance use were significantly lower among South Asians. South Asians were more likely than other foreign-born cases to have an extrapulmonary site of disease (45% vs. 33%, p<0.0001). Among culture-positive South Asian cases with a complete genotype, 20% were clustered to another NYC case compared to 37% of other foreign-born cases (p<0.0001), suggesting that most cases were due to reactivation of remotely-acquired infection. Forty-nine genotype clusters included at least one South-Asian case; epidemiologic links involving a South Asian-born case were found in 10 of these.

CONCLUSIONS: TB incidence among South Asians in NYC remains elevated. A high prevalence of extrapulmonary disease was observed and most cases were diagnosed within 5 years of U.S. entry. Although these observations can be explained by the high TB prevalence in South Asia, there is also evidence of local transmission. These results suggest the need for greater detection and treatment of LTBI among South Asians living in NYC.