SEIR model

Susceptible-Exposed-Infectious-Recovered

β = the transmission rate, the rate at which susceptible individuals come into effective contact with infectious individuals and are exposed to the virus. It incorporates both the frequency of contacts and the probability of transmission per contact.

σ = the infection rate or rate of progression from the exposed (E) compartment to the infectious (I) compartment in the SEIR model. It quantifies the speed at which individuals transition from the exposed state to becoming infectious. A higher σ value indicates a faster progression, meaning individuals become infectious sooner after being exposed.

γ = Rate of recovery or removal from the infected state.