Figure 2. The marginal distributions of exposure and host susceptibility, together with contours of their joint distribution.

The y-axis shows exposure, E, and the x-axis shows host susceptibility, α. The line w_T = αE describes the threshold of detectable infections: the minimum worm burden in an individual detectable by currently available assays. The shaded area depicts those combinations of α and E producing infection intensities above this lower limit of detection, w_t. The fraction of the population susceptible to infection at or above this threshold is that lying to the right of the line α = α*.