Increasingly studies highlight the non-stationary features of population dynamics. For instance, recent studies have shown that population dynamics can switch between different dynamics at multi-decadal scales, triggered by small environmental changes. These regime shifts were observed in different regions for different species. Transient behaviors in population dynamics have also been documented in epidemiology. Long-term changes in climate, human demography and/or social features of human populations have considerable effects on the dynamics of numerous epidemics.