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

<p>The y-axis shows exposure, <i>E</i>, and the x-axis shows host susceptibility, <i>α</i>. The line <i>w_T = αE</i> 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 <i>α</i> and <i>E</i> 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 <i>α</i> = <i>α</i>*.