Before revision:  First, we consider the movements of susceptible (S), exposed (E), and recovered (R) individuals who may get infected after movement , as well as infected (I)  . Second, the infectious contacts between people from different regions are dealt with separately from the first factor.
After revision:  First, we consider the movements of susceptible (S), exposed (E), and recovered (R) individuals who may get infected after movement , as well as infected (I) individuals . Second, the infectious contacts between people from different regions are dealt with separately from the first factor.