Identifying the direct risk source to contain epidemics more effectively

We investigate the impact of people's perceptions regarding the risk of an epidemic by analyzing the differences between local and global risk perceptions on affecting the epidemic threshold. Three issues are introduced to explain such differences: the indirect risk source, the heterogeneous global risk, and heterogeneity in individuals' intrinsic susceptibilities. When the direct risk source is completely undetected, the local risk perception tends to have no effect on the epidemic threshold, and the effect of the local risk is nearly equivalent to that of the global risk perception, thereby also suggesting a reason why global risk perception cannot affect the epidemic threshold. However, there is a surprising effect of the global risk perception: When its heterogeneity is sufficiently high, an increased epidemic threshold value sometimes may lead to a greater infected ratio.