A clustered pulmonary Tuberculosis outbreak at a technical school in Shenzhen, China.

Background: On 11 June 2025, a clustered outbreak of pulmonary tuberculosis (TB) was detected in a vocational school class in Shenzhen. Methods: A two-phase screening investigation was conducted in accordance with Chinese tuberculosis prevention and treatment guidelines. Screening procedures included symptom assessment, Interferon-Gamma Release Assays (IGRA), and chest radiography (CXR). Confirmed, clinically diagnosed, and suspected cases were identified by specialized pulmonologists following the Diagnostic Criteria for Pulmonary Tuberculosis (WS 288-2017). To assess transmission patterns, a comparative analysis of dormitory and class distributions among individuals with a positive IGRA result was performed. Additionally, whole genome sequencing (WGS) of clinical isolates was conducted to determine genetic relatedness and infer potential transmission pathways. Results: After the initial report of two cases, two rounds of screening were conducted at the school. In the first round, 453 individuals were screened. IGRA yielded valid results for 421 individuals, with a positivity rate of 9.3% (39/421); in the second round, the IGRA positivity rate was 5.1% (9/176). The abnormal CXR rates were 2.4% (11/453) and 1.1% (2/176), respectively. Across both screenings, a total of 7 cases of active tuberculosis were confirmed (including one negative for IGRA), and 42 cases of latent infection were identified. A comparative analysis of the dormitory and class distributions among individuals with a positive IGRA result showed that the IGRA positivity rate in the affected class was 62.2 % (23/37), significantly exceeding rates observed in other classes (P < 0.05). The four dormitories with the highest positivity rates were all occupied by students from Class 2302 (Room 310: 100%, Room 309: 62.5%, Room 506: 50.0%, and Room 308: 37.5%). WGS analysis revealed that five isolates belonged to the Beijing genotype and exhibited high genetic homology with minimal divergence, confirming a single clonal outbreak with slight genetic variation. Conclusions: This outbreak stemmed from intertwined factors: close contact, poor ventilation, delayed detection, and insufficient prevention. Early syndromic surveillance, enhanced health education for students and staff, improved environmental hygiene, and timely implementation of preventive treatment for latent tuberculosis infection are vital strategies for preventing and controlling TB clusters in educational settings.