Volume 19, Number 3—March 2013
Dispatch
Tuberculosis Outbreak in a Primary School, Milan, Italy
Table
Distribution of prevalence rates of TB and LTBI among current and former students at primary school, Milan, Italy, 2011*
Class | No. students | No. (%) undergoing TST | No. (%) TST positive† |
Total no. (%) active TB cases‡ | ||
---|---|---|---|---|---|---|
First test | Second and third tests | Total positive | ||||
First year | 162 | 161 (99.4) | 3 (1.9) | 0 | 3 (1.9) | 1 (0.6) |
Second year | 174 | 172 (98.9) | 47 (27.3) | 3 (1.7) | 50 (29.1) | 5 (2.9) |
Third year | 170 | 170 (100) | 11 (6.5) | 0 | 11 (6.5) | 0 |
Fourth year | 156 | 156 (100) | 30 (19.2) | 3 (1.9) | 33 (21.2) | 2 (1.3) |
Fifth year | 151 | 149 (98.7) | 57 (38.3) | 2 (1.3) | 59 (39.6) | 4 (2.7) |
Former fifth year§ | 156 | 156 (100) | 29 (18.6) | ND | 29 (18.6) | 3 (1.9) |
Transferred |
20 |
13 (65) |
3 (23.1) |
ND |
3 (23.1) |
0 |
Total | 989 | 977 (98.8) | 180 (18.4) | 8 (0.8) | 188 (19.2) | 15 (1.5) |
*Because a delay of 8–10 weeks after exposure is necessary for a positive skin test, follow-up screening was performed for students whose initial test occurred <10 weeks after exposure. TB, tuberculosis; LTBI, latent TB infection; TST, tuberculin skin test; ND, not done because initial screening was >10 weeks after exposure.
†At the first screening, 3 students refused to submit to TST; 11 refused at the second, and 11 at the third.
‡All other infections were LTBI.
§Those who were fifth-year students during the previous school year.