Epidemiological Investigation of a Tuberculosis Cluster Outbreak at a University — Changsha City, Hunan Province, China, September 2023–November 2025

What is already known about this topic?: Tuberculosis (TB) is prone to cause clustered transmission in schools. What is added by this report?: was detected (including air conditioner filters and air). Individuals with latent TB infection who receive preventive immunotherapy with Mycobacterium vaccae can develop active TB. Active cases were not identified promptly after preventive treatment, leading to renewed transmission. What are the implications for public health practice?: Guidelines should add disinfection effectiveness evaluations and cover easily overlooked items, such as air conditioner filters. Follow-up examinations for individuals with LTBI who have completed preventive treatment remain necessary, as they still face a significant risk of developing active TB.