Abstract :
In this article, we present the continuing work on a SARS model without quarantine by Hsu and Hsieh
[Sze-Bi Hsu, Ying-Hen Hsieh, Modeling intervention measures and severity-dependent public response
during severe acute respiratory syndrome outbreak, SIAM J. Appl. Math. 66 (2006) 627–647]. An “acting
basic reproductive number” ψ is used to predict the final size of the susceptible population. We find the
relation among the final susceptible population size S∞, the initial susceptible population S0, and ψ. If
ψ >1, the disease will prevail and the final size of the susceptible, S∞, becomes zero; therefore, everyone
in the population will be infected eventually. Ifψ <1, the disease dies out, and then S∞ > 0 which means
part of the population will never be infected. Also, when S∞ > 0, S∞ is increasing with respect to the
initial susceptible population S0, and decreasing with respect to the acting basic reproductive number ψ.
© 2006 Elsevier Inc. All rights reserved.
