METHODS: Sputum specimens were collected from the index patient and tested by acid-fast bacilli (AFB) smear and confirmed by nucleic acid amplification test at the Kansas Health and Environmental Laboratories (KHEL). Individuals enrolled in the same classes as the index patient were considered contacts; social contacts were obtained through interviews with the index patient; work contacts were assessed based on their work schedules. All contacts received a letter recommending testing. JCDHE held a clinic at the high school on March 11 to test all staff/student contacts; for individuals identified with more recent exposure (<8 weeks), a subsequent clinic was held on May 5. All testing conducted through JCDHE was performed using interferon-gamma release assay QuantiFERON-TB Gold and performed at KHEL.
RESULTS: The index patient’s sputum was AFB positive (grading 4+) and confirmed as TB. A total of 465 contacts were identified: 394 students, 29 staff, 5 household, 13 work, and 14 social. Of the non-student contacts, 53 (87%) were tested, and 7 (13%) tested positive. Of the 366 (93%) students tested, 32 (9%) tested positive. The class with the greatest transmission was weightlifting, with 14 of 107 (13%) positive. The amount of time spent in class with the index patient was significantly greater (p<0.001) for students testing positive (2342 hours) compared to those testing negative (1464 hours).
CONCLUSIONS: This contact investigation resulted in the identification of 43 (9.3%) TB infections. Contact investigations are inherently based on the best evidence and judgement of investigators, especially in a setting such as a high school. JCDHE opted to test all classmates of the index patient, which resulted in the identification of the weightlifting class as a high transmission location, potentially due to the exertion (and probable subsequent coughing) involved in lifting weights.