Transmission characteristics of student tuberculosis: a 12-year prospective population-based genomic epidemiological study

Abstract

Objective: To analyze the transmission characteristics of student tuberculosis (TB) from a population-wide perspective using the data from a prospective molecular epidemiology study of tuberculosis conducted in Wusheng county, Sichuan Province. Methods: From July 1, 2009 to December 31, 2020, isolates from culture-positive TB patients in Wusheng were collected for whole-genome sequencing. Genomic clusters were defined with a threshold distance of 12-single-nucleotide-polymorphisms. The risk for student patients clustering was analyzed by logistic regression. Epidemiological investigations were performed on clustered patients to clarify epidemiological links. Transmission direction was inferred using phybreak based on whole-genome sequencing and diagnosis time. Results: In total, there were 1 289 culture-positive patients in Wusheng during the study period, of which 7.6% (98/1 289) were students. Among student patients, 71.4% (70/98) were high school students, 45.9% (45/98) were grade three senior school students, and 16.3% (16/98) were junior school and senior school freshmen. The clustering rate for student patients was 59.2% (58/98), and their risk of clustering was 4.54 times higher (95%CI 2.44-8.45) than that of non-student patients. Of the transmission events that included student patients, 33.3% (11/33) were transmitted between student patients and 66.7% (22/33) were between student and non-student patients; and among the transmission events between student and non-student patients, only 22.7% (5/22) occurred at home, and the remaining 77.3% (17/22) occurred outside the home. The interval between diagnoses was 1.3 (0.4, 2.7) years for student patients and 5.3 (1.9, 6.8) years for student and non-student patients, with a statistically significant difference (Z=2.86, P=0.004). Conclusions: Student tuberculosis was mainly caused by recent transmission. Most of the transmission occurred between students and non-students, and primarily outside the home. Student tuberculosis screening strategies identified the patients earlier. The TB control and prevention strategies of school and community must be combined to achieve the desired results..