Paradoxical HCV replication kinetics. If host immune clearance forces (Ic, black arrows) reduce viral replication acutely (point A), then they must exceed viral expansive forces (Ve, grey arrows) at that point. At equilibrium (e.g. points B through D), viral concentrations (—) and, therefore, viral forces, have fallen by 102–3 hence, immune forces Ic must fall by >102–3 from A to B for equilibrium to develop. There is no evidence this happens.