Susceptible-Infected-Susceptible Virus Spread Model Based on Sparsely Distributed Crowd

A SlS (susceptible-infected-susceptible) disease spread model based on sparsely distributed crowd is proposed. In this model, the effects of crowd-density d, spread efficiency lambda and the moving of individuals on the spreading of viruses are researched. The theoretical analysis and analog simulation shows that there exist a critical value (lambdad)_c, only when the product of spread efficiency and crowd density goes beyond (lambdad)_c, can viruses spread in crowd continuously and steadily. Besides, the moving of individuals can promote the spreading of viruses. According to these results, the measures are presented to prevent the spread of viruses.