Lattice-Gas Model For The Spreading Of Infectious Diseases With Spontaneous Behavioral Changes

We present a stochastic SIR model for influenza spreading on a D-dimensional lattice, with spontaneous behavioral changes. The lattice represents the dynamic contact network of individuals. An age distributed population is placed on the lattice and moves on it. The dynamics on the lattice is governed by an attractive in- teraction between individuals belonging to the same age-class. The parameters, which regulate the pattern dynamics, are fixed fitting the data on the age-dependent daily contact numbers, fur- nished by the Polymod survey. A simple SIR transmission model with a nearest neighbors interaction and some very basic adaptive mobility restrictions complete the model. Different mechanisms for spreading awareness of the risk of contagion, which induces spontaneous behavioral changes in the population and interferes with the progression of the epidemic itself, are also added to the model. The awareness mechanisms are also calibrated on available data on awareness and concern collected by the behavioral risk factor surveillance systems. The model is validated against the age- distributed Italian epidemiological data for the influenza A(H1N1) during the 2009/2010 season, with sensible predictions for the epi- demiological parameters. We find that, whenever the accordance between the contact patterns of the model and the Polymod data is satisfactory, there is a good agreement between the numerical and the experimental epidemiological data. Furthermore, a bet- ter agreement between simulated and gathered data on awareness and concern leads to a better accordance between simulated and experimental epidemiological data.