Epidemic modeling is dominated by systems models-so-called SIR models-that describe the spatio-temporal and network dynamics of disease outbreaks. Reed-Frost, discrete-time, stochastic transmission-chain models have also been important; but, increasingly, epidemiological modelers are turning to agent-based (ABM) approaches that permit the inclusion of individual-specific characters, which may relate to the genetics of hosts or pathogens, host exposure histories, co-infections or other general health correlates. Here we introduce Nova, a graphically driven computational modeling platform for creating and running both dynamical systems and ABM models that have application both in teaching and research. Because Nova is based on the JavaScript language, all Nova models are easily transformed into Nova Online web apps. In the teaching arena, our presentation features our SIR circle games; in the research arena we discuss the application of Nova to modeling outbreaks of Ebola and measles.

Population viability analysis (PVA) is used to assess the probability that a biological population will persist for a specified period of time. Such models are typically cast as Markov processes that may include age, stage, sex and metapopulation structures, density-dependence and ecological interaction processes. They may also include harvesting, stocking, and thresholds that trigger interventions. Here we present a PVA web app that includes extensible user-selected options. Specifically, this PVA web app allows for the specification of one to ten age classes, one or two sexes, single population or metapopulation configurations with 2 or 3 subpopulations, as well as density-dependent settings for inducing region-specific carrying capacities. Movement among subpopulations can be influenced by age, metapopulation connectivity, and attractivity of regions based on the relative fitness of the youngest age classes in each region. Simulations can be carried out deterministically or stochastically, with a user-specified combination of demographic and environmental processes. This PVA web app is freely available at http://www.numerusinc.com/webapps/pva for running directly on any browser and device. It is easily modified by users familiar with the NovaModeler Software Platform.