Epidemiological Analysis of Tuberculosis Transmission, Risk Factors, and Subclinical Tuberculosis Management in a High School Outbreak, South Korea.

BACKGROUND

Tuberculosis (TB) remains a significant public health concern, particularly in congregate settings such as schools, where adolescents are at increased risk transmission. This study aimed to investigate the epidemiological characteristics, transmission dynamics, and control strategies during a TB outbreak in a South Korean high school.

METHODS

A retrospective epidemiological investigation was conducted using data from the Korea Tuberculosis Network and official outbreak reports. A total of 935 individuals-including students, staff, and household contacts-underwent screening through chest X-rays, interferon-gamma release assays (IGRAs), and chest computed tomography (CT). Genotyping of isolates was performed using spoligotyping and whole-genome sequencing (WGS). Logistic regression identified risk factors associated with TB infection.

RESULTS

Among 935 contacts, 133 (14.2%) tested positive for TB infection. In total, 30 cases of TB disease and 66 cases of latent TB infection were identified among 762 student contacts. Prolonged exposure exceeding 10 hours per week was associated with a significantly increased risk of TB infection (adjusted odds ratio = 5.91, 95% confidence interval: 3.06-11.40, < .001). Notably, subclinical TB accounted for 74.2% of active TB cases, with most detected via chest CT. WGS and phylogenetic analysis identified a distinct genomic cluster of the Beijing clade, indicating a likely single transmission chain within the school setting.

CONCLUSIONS

This outbreak highlights the importance of rapid TB diagnosis, targeted screening for high-risk groups, and advanced diagnostic tools such as IGRA and CT in identifying subclinical cases. Strengthened contact investigations and expanded preventive strategies, including household contacts, are essential for effective outbreak control.