中文说明：传染病模型中最经典的模型，包括SI模型、SIS模型和SIR模型。其中S表示易感者，I表示感染者，R表示恢复者。其中，SIR模型中，染病人群为传染的源头,他通过一定的几率把传染病传给易感人群,他自己也有一定的几率/可以被治愈并免疫,或者死亡;易感人群一旦被感染,就又成为了新的传染源。
English Description：
The most classical models of infectious disease models, including SI model, SIS model and SIR model. Where S is a susceptible person, I said infected persons, R said the restorer. Among them, SIR model, infected people as the source of infection, he through a chance to infectious disease transmitted to susceptible population, he himself also a chance / can be cured and immune, or death; susceptible population once infected, and went on to become the new source of infection.