Hopf bifurcation analysis in a delayed system for cancer virotherapy

We consider a planar delay differential equation which is motivated biologically and simulates a cancer virotherapy. The singularities and their local stability are studied using the characteristic equation. Because of biological importance, we investigate a Hopf bifurcation around the interior singularity and determine the stability of corresponding Hopf cycles by computing the normal form of the model in the direction of the Hopf bifurcation.