Inference of causality in epidemics on temporal contact networks.
Investigating into the past history of an epidemic outbreak is a paramount problem in epidemiology. Based on observations about the state of individuals, on the knowledge of the network of contacts and on a mathematical model for the epidemic process, the problem consists in describing some features of the posterior distribution of unobserved past events, such as the source, potential transmissions, and undetected positive cases. Several methods have been proposed for the study of these inference problems on discrete-time, synchronous epidemic models on networks, including naive Bayes, centrality measures, accelerated Monte-Carlo approaches and Belief Propagation. However, most traced real networks consist of short-time contacts on continuous time. A possibility that has been adopted is to discretize time line into identical intervals, a method that becomes more and more precise as the length of the intervals vanishes. Unfortunately, the computational time of the inference methods increase with the number of intervals, turning a sufficiently precise inference procedure often impractical. We show here an extension of the Belief Propagation method that is able to deal with a model of continuous-time events, without resorting to time discretization. We also investigate the effect of time discretization on the quality of the inference.
Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.|Collegio Carlo Alberto, Via Real Collegio 30, 10024 Moncalieri, Italy.|Human Genetics Foundation, Via Nizza 52, 10126 Torino, Italy.
Alfredo
A
Braunstein
Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Alessandro
A
Ingrosso
D000465:Algorithms; D001499:Bayes Theorem; D019295:Computational Biology; D004196:Disease Outbreaks; D058872:Epidemics; D053263:Gene Regulatory Networks; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method