FIG. 11: Distribution of spreading based on individual origins. The probability distribution P ( M ) of the infected percentage for the contact network of inpatients, when the epidemic starts at four nodes of different properties. The infection probability is β = 4%, which is above the critical threshold. All distributions exhibit two peaks at similar ranges every time, i.e. around M = 0 (epidemics dies very fast) and M ≃ 33%. However, the intensity of each peak differs, and in higher k -shells the majority of the realizations result in large infections, compared to the much higher ratio of zero-spreading realizations for origins of small k$_{S}$ values. the higher k$_{S}$ value in the plot, the stronger peak is at the non-zero value, and very few realizations end up at M = 0 even for smaller degrees. On the contrary, an origin with larger degree k , but smaller k$_{S}$ value results in a stronger peak at M = 0. These distributions converge quite well, and we can expect that nodes with small k$_{S}$ will in general result in a higher peak at M = 0. The above means that if an infection can reach a critical mass of nodes then it will eventually cover a significant part of the network. The low k -shell nodes cannot reach this critical mass so that the infection dies at the early stages, resulting to the strong peak at M = 0. On the contrary, the neighborhood of high k -shell nodes is favorable for sustaining an infection at early stages, allowing the system to reach this critical mass. 10 0 0.1 0.2 0.3 0.4 M 0.1 0.2 0.3 1.0 P(M) k=1 , k$_{S}$=1 k=96, k$_{S}$=63 k=96, k$_{S}$=26 k=65, k$_{S}$=63