Dynamics of an Epidemic

μ

0.0001

β

0.0001

γ

0.0001

This Demonstration shows the time behavior of solutions of the SIS model of an epidemic by means of a phase portrait. The values of the coefficients describing the system can be modified using the sliders. The population is constant and scaled to 1. If

S

denotes the density of susceptible persons and

I

the density of infected ones, the brown and gray lines are the zero isoclines for

S

and

I

, respectively, and the pink points represent the stationary states of the SIS system. Information about an outbreak or disappearance of the epidemic based on the computed value of the basic reproduction number is displayed.