An Investigation of Workplace Contacts of a Highly Contagious Tuberculosis Case-Patient - Maryland, Washington, DC, and Virginia, 2006

Background: In May 2006, the Maryland Department of Health and Mental Hygiene (DHMH) was notified of a highly contagious pulmonary tuberculosis (TB) case in a U.S.-born person, aged mid-40s, with longstanding cough. Because the patient's job as an office furniture installer involved close contact with coworkers, including travel in vans to jobsites, the workplace became the focus of this investigation. Methods: We reviewed a list of 500 employees and identified 79 coworkers potentially exposed during the 15-month infectious period, February 1, 2005–April 20, 2006. Tuberculin skin tests (TSTs) were conducted. Second-round TSTs were conducted for TST-negative contacts with recent exposure. A high rate of infection among van-riding coworkers led to expansion of the investigation to contacts with minimal exposure at 37 worksites in Maryland, Washington, DC, and Virginia. Results: TST positivity was 39% (21/54) among van-riding coworkers able to be located, including six (29%) whose TST status changed from negative to positive 8–10 weeks after the first TST. Sixty-two percent (13/21) are on treatment for latent tuberculosis infection (TLTBI). The expanded investigation at 37 jobsites revealed a 15% (21/143) TST positivity rate, with rates of 12%, 21%, and 28% in Virginia, Maryland, and Washington, DC, respectively. Thirty-three percent (7/21) are on TLTBI. No cases of active tuberculosis disease were identified. Conclusions: Prolonged infectiousness of the patient contributed to high transmission rates. Change in TST status among 29% of those infected suggests recent transmission. Workplace-based contact investigations can be effective for rapidly identifying and screening contacts.