Outbreak of Mycobacterium tuberculosis Beijing Strain in a High School in Yunnan, China

In this study, we report an investigation of a tuberculosis (TB) outbreak in a high school in China. Eleven students with active TB were identified. A culture-negative 17-year-old girl was considered as index case affected by pulmonary and meningeal TB. Screening results indicated latent TB in 32.8% of the students in the classroom of index case, whereas a significantly decreased prevalence of TB infection was found among students on the same floor, ranging from 1.3 to 8.2%. Genotyping revealed that all the Mycobacterium tuberculosis (MTB) isolates belonged to Beijing spoligotype international types 1 (SIT1). In conclusion, a diagnostic delay for the culture-negative index case played an important role in the transmission of Beijing genotype MTB strain in the boarding school in Yunnan. The separate locations of classrooms and sufficient air ventilation contributed to the significant difference in proportions of TB infection between classmates and other students in this outbreak.