Finally, in Figure 9 , we present scenarios in which each of four other parameters are modified from the baseline values of Figure 3A , assuming 40 contact tracings (ring vaccinations) are possible per day (line a in the figure) . Specifically, we assume that severe smallpox (hemorrhagic and flat) on average takes four times longer to diagnose and isolate than ordinary smallpox (case b), Table 4 : Containment of severe smallpox at different levels of contact finding. The first three columns are assumed levels for the probability of finding a household contact, the probability of finding a workplace/social (W/S) contact, and for the number of contact tracings/ring vaccinations possible per day; the last two columns express (as percentages) the resulting probability of containment given the assumed contact finding probabilities and contact tracing capacities; two containment probabilities are given: the containment probability when only contacts of cases are traced (first column, "Contacts"), and the containment probability when contacts of contacts of cases are traced in addition to the contacts of cases (second column, "Contacts of Contacts"). All other parameters are the same as in Figure 3A . that no one in the population has prior vaccination protection (from before the discontinuation of routine vaccination, case c), that 10% more smallpox is too mild to diagnose (but still contagious, case d) compared to baseline, and finally that the vaccine is completely ineffective (case e). Each of these scenarios will be discussed further below.