Spatial-temporal distribution of genotyped tuberculosis cases in a county with active transmission

Saroochi Agarwal, Duc T. Nguyen, Larry D. Teeter, Edward A. Graviss

Harris County, Texas is the third most populous county in the United States and consistently has tuberculosis rates above the national average. Understanding jurisdictional epidemiologic characteristics for the most common Mycobacterium tuberculosis genotyped clusters is needed for tuberculosis prevention programs. Our objective is to describe the demographic, laboratory, clinical, temporal and geospatial characteristics for the most common Mycobacterium tuberculosis GENType clusters in Harris County from 2009 to 2015. We analyzed data from the Centers for Disease Control and Prevention (CDC) Tuberculosis Genotyping Information Management System (TB GIMS). Chi-square analyses were used to determine associations between selected clusters and specific characteristics of interest. Geographical Information System (GIS) point density and hot spot maps were generated and analyzed with ArcGIS 10.4. In Harris County from 2009 to 2015, 1655 of 1705 (97.1%) culture positive tuberculosis cases were genotyped and assigned a GENType, and 1058 different GENTypes were identified. The analyzed genotype clusters represent 14.1% (233/1655) of all genotyped cases: G00010 (n = 118), G00014 (n = 38), G00769 (n = 33), G01521 (n = 26), and G08964 (n = 18). Male gender (p = 0.002), ethnicity (p < 0.001), homelessness (p < 0.001), excessive alcohol use (p = 0.002), and U.S.-birth (p = 0.004) were associated with the 5 GENTypes. Hot and cold spots were identified as geographic areas having high and low TB incidence. Of more than 1000 distinct GENTypes identified in Harris County, there were 5 common Mycobacterium tuberculosis GENType clusters seen from 2009 to 2015. The common genotypes were observed primarily in U.S.-born populations despite the large foreign-born population residing in Harris County. GENType was significant distributed spatially and temporally in Harris County in the analyzed time period indicating that there may be outbreaks caused by transmission.