Tuberculosis control in schools represents a critical public health priority in China; however, outbreaks continue to pose significant challenges. From 2008 to 2018, the reported incidence rate of TB among students was approximately one-third to one-fourth that of the general population, exhibiting an initial decline followed by an upward trend (1). The rate declined from 27.92 per 100,000 population in 2008 to 13.30 per 100,000 in 2015, then gradually increased to 17.97 per 100,000 in 2018 (1). The reported TB incidence among students was highest in the western region and lowest in the eastern region (2). The outbreak described in this study occurred in Guangxi, a province in southwest China with a reported TB incidence rate of 67.54 per 100,000 in 2023.
Tuberculosis outbreaks typically occur among individuals living in close-contact environments, with schools being common sites of transmission. Outbreaks usually occur within the same class or dormitory. However, this outbreak exhibited distinct epidemiological characteristics and demonstrated high clustering patterns. With the exception of two staff members, all PTB cases were epidemiologically linked, indicating that this represented a cross-household, cross-school-grade, cross-junior/senior-high-school clustered outbreak. In this outbreak, five cases were Hr-TB. Although the management of isoniazid-resistant tuberculosis and drug-sensitive tuberculosis during an outbreak follows similar protocols, their treatment regimens and public health implications differ substantially. Compared with drug-sensitive tuberculosis patients, patients with Hr-TB demonstrate higher treatment failure rates (11% vs. 1%), higher recurrence rates (10% vs. 5%), and higher rates of acquired resistance (8% vs. 0.3%) (3). Molecular epidemiological studies have been widely utilized in contact tracing to understand person-to-person transmission patterns. Spacer oligonucleotide typing (spoligotyping) and MIRU-VNTR typing (mycobacterial interspersed repetitive units-variable number of tandem repeats) are commonly employed typing methods, but they are unsuitable for confirming transmission events in China, due to their limited ability to identify transmission chains in most TB outbreak scenarios. Several studies have demonstrated the utility of whole-genome sequencing (WGS) in epidemiological investigations and have suggested that WGS offers superior discriminatory power compared to spoligotyping and VNTR typing (4–6). In this outbreak, we employed WGS in our epidemiological investigation and demonstrated extremely high genetic similarity (<6 SNPs) between isolates. These results provided evidence that transmission may have begun during junior high school and originated from a single recent transmission source. However, it remains impossible to accurately determine the onset time of the identified cases, and thus the exact transmission chain cannot be definitively established. Based on epidemiological associations and the WGS results, we conclude that the primary transmission chain of this outbreak most likely originated within a household and subsequently spread from the index case to close contacts, including classmates, roommates, and the teacher. The remaining two cases, involving school staff, showed no obvious epidemiological links with the aforementioned 16 cases and may represent independent infections from other sources. As no bacterial isolates were obtained from these cases, further molecular analysis was not possible.
LTBI represents a persistent immune response to M. tuberculosis infection without clinical manifestations or radiological evidence of active disease (7). Approximately 23% of the global population harbors LTBI. Among infected individuals, 5% to 10% will progress to active tuberculosis during their lifetime. Given the substantial prevalence of LTBI, even a modest progression rate to active disease could significantly impact tuberculosis control efforts. Consequently, preventive treatment was administered to selected cases in this outbreak.
The fusion protein skin test or tuberculin skin test serves as a standard screening method; however, false-negative results may occur in certain cases. This limitation may have contributed to the failure to detect the index patient during school enrollment screening. Furthermore, multiple additional factors likely contributed to this public health emergency. First, the diagnosis of the index case experienced significant delay. Second, daily symptom monitoring and student absenteeism tracking failed to identify symptomatic students. This outbreak underscores the critical importance of household contact screening, particularly when household members include students or teachers. Simultaneously, the outbreak has highlighted the need to enhance the quality and effectiveness of freshman entrance physical examinations. Essential routine practices such as monitoring and documenting illness-related absenteeism, conducting daily morning and afternoon health screenings, and providing comprehensive health education require strengthening and standardization.