Pulmonary Tuberculosis Outbreak in a High School, China

This study reports an outbreak of Tuberculosis (TB) in a high school in Hunan province, China during January 2017-April 2018. Contact investigation and TB screening were conducted through symptom screening, tuberculin skin testing, chest radiography and smear examination. Identification of positive isolates and drug susceptibility phenotype were assessed by standard method. Mycobacterial Interspersed Repetitive Units-Variable Number Tandem Repeats (MIRU-VNTR) and Whole Genome Sequencing (WGS) were performed to investigate the relationships among the positive isolates. A total of 90 students and one teacher were diagnosed active pulmonary TB among 2908 students and 188 staff, with an attack rate of 2.94%. Thirteen positive isolates were identified as drug susceptible Beijing family of Mycobacterium tuberculosis. Results of MIRU-VNTR typing and WGS revealed two clones of Mycobacterium tuberculosis circulating during outbreak. One hundred and twenty-nine Single Nucleotide Polymorphisms (SNPs) discriminated the isolates in two clusters; the maximum number of SNPs between any pair of isolates in each cluster was five or fewer. Our findings highlight the importance of early identification and isolation of the TB cases to prevent spread of TB. WGS provides better resolution than MIRU-VNTR to identify recent transmission in TB outbreak.