[Molecular Epidemiological Analysis of Tuberculosis Transmission in Households in Republic of Korea, 2016-2024]

Tuberculosis (TB) is an airborne infectious disease transmitted through droplets from coughing or sneezing. The risk of Mycobacterium tuberculosis complex infection is high among close contacts sharing living or working spaces with patients with TB. The Korea Disease Control and Prevention Agency conducts close contact investigations targeting household contacts to prevent TB spread through early detection and treatment. As part of these investigations, TB strain genotyping is performed to analyze the molecular epidemiological links.

From 2016 to 2024, the epidemiological information and molecular epidemiological characteristics of 20 suspected cases of household transmission involving 43 individuals were analyzed following their identification through investigations. Spoligotyping and 24-locus mycobacterial interspersed repetitive unit-variable number tandem repeat were used for TB genotyping.

Each case of suspected intrafamilial TB transmission involved 2-3 patients, including parent-child (15 cases), sibling (4 cases), and cohabitant (1 case) transmissions. At the time of index notification, 12 cases (60%) involved cohabitation, while 7 cases (35%) did not. The time difference between the index and additional case notifications ranged from 2 to 2,241 (average 291) days. The TB genotyping results confirmed molecular epidemiological links between each suspected case. Among the 20 cases, 5 cases (involving 10 individuals) presented drug-resistant TB, with 4 cases of multidrug-resistant TB and 1 of extensively drug-resistant TB. Drug resistance profiles were consistent within each case.

Based on the TB genotyping and contact investigations, cases of TB transmission within the household appear to have epidemiological links. To support the national TB control efforts, we plan to continue molecular epidemiological analyses of household transmission and outbreak cases.