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The quasi-stationary distribution of the closed endemic sis model

Published online by Cambridge University Press:  01 July 2016

Ingemar Nåsell*
Affiliation:
The Royal Institute of Technology, Stockholm
*
Postal address: Department of Mathematics, The Royal Institute of Technology, S-l0044 Stockholm, Sweden.

Abstract

The quasi-stationary distribution of the closed stochastic SIS model changes drastically as the basic reproduction ratio R0 passes the deterministic threshold value 1. Approximations are derived that describe these changes. The quasi-stationary distribution is approximated by a geometric distribution (discrete!) for R0 distinctly below 1 and by a normal distribution (continuous!) for R0 distinctly above 1. Uniformity of the approximation with respect to R0 allows one to study the transition between these two extreme distributions. We also study the time to extinction and the invasion and persistence thresholds of the model.

Type
General Applied Probablity
Copyright
Copyright © Applied Probability Trust 1996 

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