A SIMULATION-MODEL FOR OCCUPATIONAL TUBERCULOSIS TRANSMISSION

A simulation model of tuberculosis (TB) transmission among hospital em ployees is described. A hypothetical cohort of 1000 workers was divide d into low-, medium-, and high-risk groups. The number of TB patients admitted daily was treated as a Poisson random variable. A patient imp arted a daily infection risk that was identical for all workers within a risk group but that varied between risk groups. In some scenarios, infected employees were assigned a daily risk of developing TB disease . If disease developed, the individual remained on the job for 3 calen dar weeks and imparted a substantial infection risk to 25 close contac ts. Simulations were run over 5-year intervals. Cumulative infection i ncidence increased over time and with more TB patients admitted. Given a scenario in which there were 600, 300, and 100 susceptibles in the low-, medium-, and high risk groups, respectively, 50 TB patients admi tted annually and accounting for disease among infected employees, at 5 years there were approximately 100 primary infections (due to infect ion by patients), 40 secondary infections (due to infection by disease d coworkers), five primary disease cases, and two secondary disease ca ses. The input parameter values and simulation outcomes were reasonabl y consistent with the sparse information reported in the literature.