  A mathematical modeling of Hepatitis C Virus (HCV) dynamics has been
presented in this paper. The proposed model, which involves four coupled
ordinary differential equations, describes the interaction of target cells
(hepatocytes), infected cells, infectious virions and non-infectious virions.
The model takes into consideration the addition of ribavirin to interferon
therapy and explains the dynamics regarding biphasic and triphasic decline of
viral load in the model. A critical drug efficiency parameter has been defined
and it is shown that for efficiencies above this critical value, HCV is
eradicated whereas for efficiencies lower this critical value, a new steady
state for infectious virions is reached, which is lower than the previous
steady state.
