Reported Tuberculosis in the United States, 2018


Genotype Clusters

TB genotyping uses laboratory-based analyses to characterize a small portion of the genetic material of bacteria belonging to the Mycobacterium tuberculosis complex.

TB genotype clusters are defined in this report as ≥2 cases with matching genotypes in the same county or county equivalent area during a 3-year time period. Clusters are classified into alert levels on the basis of a log-likelihood ratio (LLR) calculation; clusters with an LLR of 5–<10 are classified as a medium alert level, and clusters with an LLR ≥10 are classified as a high alert level.

Cases that are part of the same genotype cluster are more likely to be related by transmission.