where pol N,1 is the concentration of the polymerases located at the first segment of the N gene ( Figure 9C) , k e,pol is the elongation rate of polymerase, / N is the attenuation factor for N gene, n sec,N is the total number of the segments of N gene, and l mRNA,N is the length of N mRNA (Table 2 , [28, 29] ). The genome segments are continuously charged with incoming polymerases and discharged with outgoing polymerases with a rate of k e,pol (Equations 7-9). If the polymerase input to the leader region of the genome is decreased owing to a lack of free polymerases, then the polymerase concentrations downstream of the leader region will be subsequently reduced ( Figure 9C ). There are conserved intergenic sequences involved in letting a fraction of viral polymerases release from the genome template at intergenic sections during transcription, which is so-called partial transcription termination or attenuation ( Figure 9C ) [18, 19] . Because the transcription is initiated from the 39 end promoter, the attenuation mechanism causes genes more proximal to the 39 end to be more highly expressed, which ultimately leads to an unequal concentration distribution of viral mRNAs. The extents of partial transcription termination are quantified by the attenuation factors, / i , in our model ( Figure 9C ). These are 0/0.25/0.25/0.25/0.05 for leader-N/N-P/ P-M/M-G/G-L intergenic regions, respectively [18, 19, 26, 27] . / i fraction of polymerases are released at intergenic region i. With Equations 7-9, we simulate the polymerase flux into each gene segment, which is proportional to the elongation rate of polymerase, but inversely proportional to the extent of attenuation: dpol i;j dt ¼ k e;pol ðð1 À / i Þ n sec;iÀ1 l mRNA;iÀ1 pol iÀ1;nsec;iÀ1 À n sec;i l mRNA;i pol i; j Þ j ¼ 1; i ¼ P; M; G; L ð8Þ dpol i;j dt ¼ k e;pol n sec;i l mRNA;i ðpol i; jÀ1 À pol i; j Þ j 6 ¼ 1;