Abstract:

Objective To analyze the epidemic of clustered tuberculosis (TB) in a school setting, and to explore the significance of chest X-ray follow-ups in the disposition of TB epidemic outbreak. Methods A total of 21 patients with active TB were found in a vocational training school in Daxing District, Beijing from March 17th to April 17th 2016, which was an epidemic of clustered TB outbreak. After the outbreak, 3490 teachers and students received tuberculin (PPD) skin test and chest X-ray screening, and then 3 sputum smears and 2 sputum mycobac-terium culture examinations were performed on each of the 65 cases who appeared to have abnormal chest X-ray results, 39 cases were diagnosed with TB; 313 cases with strongly PPD positive reactions were treated with preventive chemotherapy. The first chest X-ray follow-up was made for the school teachers and students (except for the confirmed patients with active pulmonary TB) 3 months after the disease outbreak. Thereafter 3 chest X-ray follow-ups were carried out and the intervals were 3, 6 and 8 months respectively. Chest radiographs of newly diagnosed patients were printed out during each follow-up and compared with their previous chest imaging data so as to observe whether there were any changes or omissions in the lung lesions, and the relevant records were made. SPSS 18.0 software was used for data analysis,the comparison of count data rate was done by χ² test and P<0.05 was regarded as statistically significant. Results A total of 162 cases with active TB were found in the outbreak. The detection rate was 1.7% (60/3490) when the epidemic occurred, and the detection rates of the 4 follow-ups were 1.6% (50/3031), 0.7% (19/2650), 0.8% (15/1860) and 0.2% (2/1134) respectively. The detection rate in the first follow-up (1.6%) was significantly higher than that of the other 3 follow-ups (that was 0.7%, 0.8% and 0.2%) (χ²=23.73, P<0.05). Seventeen cases were delayed to be detected in the 4 follow-ups, of which 15 cases were found in the first follow-up, while 1 case was found in the second and third follow-up respectively, no delayed cases were found in the fourth follow-up. So the detection rates of the delayed cases in the 4 follow-ups were 30.0% (15/50), 5.3% (1/19), 6.7% (1/15) and 0.0% respectively, and the detection rate of the delayed cases in the first follow-up was significantly higher than the other 3 follow-ups (χ²=7.89,P<0.05). Conclusion It is able to detect the new cases and omissive cases timely in the follow-ups after the outbreak of tuberculosis, especially 3 months after the outbreak, which is effective for the control of tuberculosis epidemic in a school setting.

Key words: Tuberculosis, pulmonary, Schools, Disease outbreaks, Radiography, thoracic, Contact tracing, Outcome assessment (health care)