Cartoon model of the effect of temperature on polymerase-RNP interactions and viral RNA synthesis. The size of arrow represents the relative rate of each process. At 37°C, polymerase-vRNA complexes are stable and catalyse the synthesis of mRNA and low amounts of cRNA. Polymerase-cRNA complexes show a moderate rate of dissociation and reassociation that permits high levels of vRNA synthesis. At 41°C, polymerase-vRNA complexes are less stable but still permit high level mRNA synthesis and near normal cRNA synthesis. However, the high rate with which polymerase-cRNA complexes dissociate does not permit efficient vRNA synthesis.