Abstract: Objective  To analyze the TB aggregation epidemic situation of a school TB outbreak in Ji’ning city of Shandong.    Methods  We performed tuberculin skin test and symptom screening to 3254 students for detecting latent and active TB in the school. The M. tuberculosis isolates were genotyped by 24-locus MIRU-VNTR. Using the logistic regression analysis, we analyzed the relationship between exposure levels to the culture positive cases and the possibility of being diagnosed as latent or active TB.   Results  The rate of latent tuberculosis infection was 28.8% in the middle school students, a total of 10 active cases were diagnosed, among which 3 of them were culture positive. The results of 24 points MIRU-VNTR genotyping showed that two isolates were clustered. One isolate had three different hypervariable loci: Mutub4, Mtub21 and QUB-26. The logistic regression analysis indicated that being the same class or the same grade with the three culture positive cases are risk factors for both latent and active TB.   Conclusion  The three culture positive cases may caused certain level of transmissions, which may lead to the outbreak of the other seven active TB cases. Therefore, the timely diagnosis and effective treatment of student cases and timely TB screening are important to control the TB outbreaks in schools.

Key words: Tuberculosis,pulmonary/epidemiology, Disease out breaks, Tuberculosis,pulmonary/transmission, Genotype, Epidemiology,molecular, Epidemiologic studies