Fig 6. Bifurcation of parameter K₄ and ρ for R_IC, [Cytokines] and [T_effector] on day 30 after infection.

a-c for parameter K₄ when the value of ρ is taken as 0.0025. d-f for parameter ρ when the value of K₄ is taken as 84. Red solid circles and blue squares represent severe and mild-moderate cases, respectively. The other parameters are default and are shown in Table A in S1 Text. The gray region indicates a bistable status for mild-moderate and severe cases.