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Reported Tuberculosis in the United States, 2022
Molecular Surveillance
TB genotyping is a laboratory-based approach used to analyze genetic material (e.g., DNA) of Mycobacterium tuberculosis; characterizing distinct genetic patterns facilitates distinguishing certain M. tuberculosis strains from others.
This is the first year ÐÇ¿ÕÓéÀÖ¹ÙÍø is reporting genotyping results using wgMLSType (whole-genome multilocus sequence type), a typing method based on whole-genome sequencing, instead of conventional genotyping methods (e.g., spoligotyping). Genotype surveillance coverage, defined as the percentage of culture-positive TB cases with a genotyped isolate, was 96.0% in 2022.
This report considers a TB case clustered if the wgMLSType of the case’s isolate matched one or more other cases’ isolate in the same county or county-equivalent area during the 3-year period of 2020–2022. ÐÇ¿ÕÓéÀÖ¹ÙÍø generates cluster alerts (i.e., medium alert and high alert) based on the degree of geospatial concentration of cases with matching wgMLSType within the same county or county-equivalent area compared with the concentration of the wgMLSType outside of the given county or county-equivalent. ÐÇ¿ÕÓéÀÖ¹ÙÍø reviews medium and high alerts weekly for possible programmatic follow-up.
The percentage of clustered genotyped cases during 2019–2021 (19.2%) based on conventional genotyping methods in last year’s report compares with 16.9% clustering during 2020–2022 based on whole-genome sequencing methods.
- Clustering percentages were higher among U.S.-born persons during 2020–2022 compared with 2019–2021 (37.1% and 34.6%, respectively) and lower among non-U.S.–born persons (10.0% and 13.5%, respectively).
- The number of clusters reported nationally declined in 2020–2022 (987) compared with 2019–2021 (1,241), a 20.5% reduction from last year’s report.
ÐÇ¿ÕÓéÀÖ¹ÙÍø identifies genotype-matched clusters, which can represent TB outbreaks, using geospatial analysis to identify unexpected clustering of TB cases within a defined time period. TB control programs can use this cluster detection information to help allocate and prioritize resources for investigation and intervention for specific cases.
ÐÇ¿ÕÓéÀÖ¹ÙÍø’s primary outbreak detection method identifies higher than expected geospatial concentrations of a TB genotype in a specific county, compared with the national distribution of that genotype. A log-likelihood ratio calculation characterizes genotype clusters into one of three alert levels: no-alert, medium-level alert, or high-level alert.
Among clustered cases the percentage that were in medium- or high-level alert clusters increased during 2020–2022 compared with 2019–2021 (65.7% and 38.3%, respectively).
Percentages of clustered cases in alerted clusters varied across population subgroups during 2020–2022.
- By origin of birth, percentages of clustered cases in alerted clusters were higher among U.S.-born persons (72.8%) compared with non-U.S.–born persons (56.9%).
- By race/ethnicity, percentages were highest among American Indian or Alaska Native persons (96.1%) and lowest among Hispanic or Latino persons (54.2%).
- By age group, percentages were highest among persons aged 0–4 years (79.2%) and lowest among persons aged 65 years or older (60.5%).
- Among risk factors for TB disease, persons residing in correctional facilities at diagnosis had the highest percentage in alerted clusters (75.0%).
Learn more in the Executive Commentary.
