Optimal utilization of genomic nucleocapsids. Genomic nucleocapsids can either be used as templates for RNA synthesis or they may be incorporated into progeny virions. Their fate depends on levels of polymerase and M protein, which respectively favor RNA synthesis or virion production pathways, as well as on the extent to which association of the nucleocapsid with M protein will dominate over association with polymerase, described with the parameter S cond in our model (Table 1) . Because both RNA synthesis and virion production are essential processes of the infection, extreme values of S cond that favor one process over the other will be [49] S pol ¼ 170 nt Strength of anti-genomic promoter relative to that of genomic promoter a S prom ¼ 5.43 Rate constant ratio of the associations of M protein and polymerase with the genomic nucleocapsid a S cond ¼ 6.2 3 10 À5