现有四个城市为 SARS 疫区。要求该仿真软件对未来一段时间内SARS 的感染趋势、 SARS 感染与旅行活动之间的关系等进行仿真。-SARS infected areas of the four existing cities. Require the simulation software for some time the trend of infection SARS, SARS infection and the relationship between the activitie