REFINING A RISK MODEL FOR OCCUPATIONAL TUBERCULOSIS TRANSMISSION

The traditional Poisson probability model for airborne Mycobacterium t uberculosis (M. tb) infection, also termed the Wells-Riley equation, c an be modified to account for a health ca re worker's use of respirato ry protection. It was previously shown that the beta distribution on t he interval [0,1] is a good descriptor of respirator penetration value s experienced by an individual worker from wearing to wearing, and of average respirator penetration values experienced by different workers . Based on the premise that the gamma distribution can reasonably desc ribe the time-varying M. tb aerosol exposure levels experienced by hea lth care workers, analytical I solutions are presented for an individu al worker's cumulative risk of infection, and for the worker populatio n mean cumulative risk of infection, with and without use of respirato ry protection. The gamma distribution is shown to be similar to the lo gnormal in describing right-skewed distributions of aerosol exposure c oncentrations on the interval [0,infinity).