Whole-genome sequencing and epidemiological analysis of a tuberculosis outbreak in a high school of southern China

Tuberculosis (TB) is a serious global public health threat, and school-clustered outbreaks are common. Here, we report a TB outbreak in a high school in southern China, which was confirmed and characterized by traditional epidemiological methods and whole-genome sequencing (WGS) of Mycobacterium tuberculosis isolates. All students and faculty (n = 287) were screened by chest X-ray for active TB. TB was diagnosed in 28 patients, according to laboratory confirmation (n = 11) of Mycobacterium tuberculosis, sputum/bronchoalveolar fluid culture, smear, or TB-Xpert. Clinically diagnosed TB cases (n = 17) were further defined by the interferon-γ releasing assay or clinical and radiological findings. Twenty-five of the affected individuals were 12th grade students aged 16 to 19 years; among them, 24 patients were male and 21 had visited the internet café near the school. WGS and phylogenetics analysis confirmed that the outbreak was mainly caused by a super transmission strain of lineage 4.2, which was susceptible to all tested antibiotics. After a treatment regimen of 9 to12 months, all 28 patients were cured. This study highlights the key factors contributing to school-clustered TB outbreaks mainly derived from a single super transmission strain, along with effective interventional measures to prevent a larger scale outbreak.