The Influence of Host Susceptibility on Epidemic Tuberculosis

Tuberculosis (TB) is the leading cause of death due to infectious disease world-wide, with three million deaths per year and as many as two billion latent but infected carriers. A number of factors likely contribute to differences in tuberculosis levels as observed throughout the world. The host immune response plays a role, and evidence suggests correlations between susceptibility to TB and host genes involved in immune responses. We present a modified S-I-R model describing a TB epidemic in a population comprised of individuals who are either inherently more susceptible to TB or neutral. As many of the studies associating susceptibility to active TB have been performed in India, we base model demographics on these studies. Our results indicate that both prevalence and incidence of disease are greatly increased by a subpopulation with inherent susceptibility to active TB. In addition, simulations suggest that there are multiple mechanisms of action of the susceptibility allele at both the host and population level.