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From the same source or multiple sources, the pathogen may trigger multiple infection processes, and each infection process will cause different theoretical incidence. However, some of the previously infected individuals may be re-infected in the ongoing infection process, that is, the previous and ongoing infections overlap. The higher the previous incidence, the greater the subsequent infections overlap. In the total incidence calculation, the overlap should be removed. In this study, an infection overlap model, based on the probability principles, was proposed as the following: A ( ti )= B ( t 1), i =1; A ( ti )= B ( ti )(1-Σ j =1 i -1) A ( tj )), i =2,3,..., where A ( ti ) is the newly occurred infection incidence in i -th infection, ti is the time for occurrence of i-th infection, and B ( ti ) is the theoretical incidence calculated. The total incidence dynamics is thus: S ( ti )=Σ j =1 i A ( tj ), i =1,2,3, ... The model can be used as a fundamental model frame for the epidemic with repeated re-infections by pathogens.
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