Speaker
Description
Reinfection is known to induce complex epidemiological dynamics (e.g. sustained oscillation) due to the time-series change in susceptibility. The simplest model describing reinfection shows three epidemiological dynamics; disease-free, epidemic and endemic. These three dynamics can be classified by two reproduction numbers, basic reproduction number and reproduction number by only reinfection. However, the simplest model takes into account only two variations of susceptibility, susceptibility at first infection and second or later infection. To relax this assumption we construct a parsimonious model describing three susceptibilities, i) susceptibility at first infection, ii) partial protection at second or later infection and iii) perfect protection at second or later infection. This model demonstrates an interesting dynamics, outbreak occurs after the temporal decrease in the number of infected individuals. We named this dynamics as "delayed outbreak". Basic reproduction number cannot capture outbreak potential of this dynamics. Our model is too simple to understand rich dynamics induced by heterogeneity in susceptibility, for example, endemic situation is not captured in this model. To understand the dynamics with heterogeneity in susceptibility, we expand our model to a model describing the transition of susceptibility by reinfection. We confirmed that "delayed outbreak" is robust if the heterogeneity in susceptibility against reinfection exists.
