Characterizing tuberculosis genotype clusters along the United States-Mexico border

We examined the growth of tuberculosis (TB) genotype clusters during 2005-2010 in the United States, categorized by country of origin and ethnicity of the index case and geographic proximity to the US Mexico border at the time of TB diagnosis. Nationwide, 38.9% of cases subsequent to Mexico-born index cases were US-born. Among clusters following US-born Hispanic and US-born non-Hispanic index cases, respectively 29.2% and 5.3% of subsequent cluster members were Mexico-born. In border areas, the majority of subsequent cases were Mexico-born following US-born Hispanic (56.4%) and US-born non-Hispanic (55.6%) index cases. These findings suggest that TB transmission commonly occurs between US-born and Mexico-born persons. Along the US Mexico border, prioritizing TB genotype clusters following US-born index cases for investigation may prevent subsequent cases among both US-born and Mexico-born persons.