Extinction and quasi stationarity in the stochastic logistic SIS model This volume presents explicit approximations of the quasi stationary distribution and of the expected time to extinction from the state one and from quasi stationarity for the stochastic logistic SIS model. Qualitatively different approximations are derived separately in three different parameter region and then combined into a uniform approximation across all three regions. Subsequently the results are used to derive thresholds as functions of the population size N. P. [4] of cover