Abstract:

Objective To analyze the screening close contacts of a tuberculosis patient in a kindergarten in the downtown area of Shanghai, and to provide references for improving the prevention and control of tuberculosis in nurseries and kindergartens. Methods Epidemiological screening, including suspected symptoms screening, latent Mycobacterium tuberculosis infection (IGRA), chest X-rays or CT scans, and sputum smears and cultures were conducted on February 15, 2019 and March 14, 2019 among 128 close contacts of a staff member who was diagnosed as tuberculosis on January 14, 2019 in a kindergarten in downtown Shanghai. The latent infection status of close contacts with different characteristics (gender, BCG vaccination status, suspected pulmonary tuberculosis symptoms, recent medical history of respiratory disease, and exposure level) was analyzed. Results Among the 128 close contacts, 107 (83.59%) were children and 21 (16.41%) were faculty. The positive rate of suspected tuberculosis symptoms was 5.47% (7/128), which were 5.61% (6/107) in children and 4.76% (1/21) in faculty. In the two screening tests, 125 close contacts (3 children refused to be tested) were tested for IGRA, and 11 cases (8.80%) were positive, including 4 children (3.20%) and 7 teaching staff (5.60%). The detection rate of tuberculosis was 0.78% (1/128), and the total latent infection rate was 8.06% (10/124, excluding 1 case confirmed and 3 children without IGRA test). The latent infection rate of children (2.91%, 3/103) was significantly lower than that of teaching staff (33.33%, 7/21), and the difference was statistically significant (χ²=21.773, P=0.000). Seven teaching staffs of latent infection were followed up by chest film at the end of 3, 6 and 12 months, and 3 children of latent infection were treated with prophylactic anti-tuberculosis drug intervention for 3 months. After one year follow-up observation, there was no patient with secondary tuberculosis. Univariate analysis showed that the latent infection rate of BCG vaccinated patients (5.13%, 6/117) was statistically significant compared with that of non-vaccinated patients (4/7) (Fisher’s exact probability method, P=0.001). The latent infection rate of high exposure level persons (17.07%, 7/41) was significantly higher than that of medium exposure level persons (3.61%, 3/83), and the difference was statistically significant (χ²=5.012, P=0.025). Conclusion Health examination of staff in nurseries and nursery institutions should be strengthened, and IGRA testing should be actively carried out to screen close contacts of tuberculosis patients, especially those without BCG vaccination history and high exposure. It is of great significance to take preventive therapy or follow up with radiography in the patients with latent Mycobacterium tuberculosis infection for the prevention of secondary tuberculosis.

Key words: Tuberculosis, pulmonary, Contact tracing, Latent tuberculosis, Kindergarten