where pol r,n,i,1 and pol r,n,i-1,nsec,i-1 are the concentrations of the replicating polymerases on the first segment of gene i, and on the last segment of gene iÀ1, respectively. The level of polymerases that scan through the whole genome (pol tr ) determines the amount of newly synthesized anti-genomic nucleocapsids, (þ)nc: dpol tr dt ¼ k e;pol n sec;i l mRNA;i pol r;n;i; j À pol tr l tr i ¼ L; j ¼ n sec;L ð17Þ dðþÞnc dt ¼ k e;pol encap pol tr l tr À k d;nc ðþÞnc ð18Þ