| Variables | Description |
| St | Susceptible in t |
| Et | Exposed in t |
| InSt | Infectious but not sick in t |
| SIt | Infectious and sick in t |
| SnIt | Sick and non-infectious in t |
| Rt | Recovered in t |
| Tt | Death cases in t |
| R0 | Basic reproductive rate |
| Nt | Net reproductive rate in t |
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