HIGH-RATE OF TRANSMISSION OF TUBERCULOSIS IN AN OFFICE - IMPACT OF DELAYED DIAGNOSIS

We identified two cases of tuberculosis (TB) in office co-workers in M elbourne, Victoria, Australia; the Mycobacterium tuberculosis isolates were found to be identical with use of restriction fragment length po lymorphism. Contact tracing was performed for 195 of 210 workers by me ans of the tuberculin skin test. Risk of infection was assessed accord ing to a number of variables. Office contacts were exposed to infectio us TB for 4 months; at least 24% of employees were infected. There was an association between sitting in proximity to the case during the pe riod of exposure (OR, 4.24; 95% CI, 1.06-19.67). On-site workers had a higher risk of being infected (OR, 5.48; CI, 1.51-23.54) than did vis iting workers. Workers in this office were exposed to open pulmonary T B for prolonged periods. The prevalence of TB infection (24%) among th ese workers was high compared with the infection rate (2%-7%) in the g eneral community. Delay in diagnosis was the major factor responsible for the spread of TB in this office.