1. A tangible computer-readable medium encoded with instructions for creating a social network stochastic directed graph model based on a stochastic directed graph, wherein execution of said “social network stochastic directed graph model” by one or more processors causes said “one or more processors” to perform the steps comprising: a. using an activity generator for creating agents in the stochastic directed graph to represent a population stratum; b. selecting said agents proportionally to the size of said population stratum and representative activities associated with said population stratum, said agents having a dynamically adjustable and time-varying conditional probability attached to said activities indicating the likelihood of interaction between said agents with at least one other agent or actor; c. accumulating outcomes for said interaction, said outcomes including benign outcomes and acute outcomes; and d. estimating a multinomial probability distribution based on said outcomes.