This is a simplified model of an epidemic. The main factor, the rate a disease is able to spread through a susceptible population, is called the basic reproductive number, or R0.

The basic reproduction number, R₀, holds the key to how large that proportion is. The higher the basic reproduction number, the higher the immune proportion of the population needs to be.

The article also presents fundamental properties of the basic reproduction number (Ro) for their specific model. Ro is the expected number of secondary cases due to a single infection.

Called the R-naught, or basic reproductive number, the model predicts the average number of susceptible people who will be infected by one infectious person.

WAN-TONG LI, FEI-YING YANG, TRAVELING WAVES FOR A NONLOCAL DISPERSAL SIR MODEL WITH STANDARD INCIDENCE, The Journal of Integral Equations and Applications, Vol. 26, No. 2 (SUMMER 2014), pp. 243-273 ...

Abstract: The reproduction number of an infectious disease, such as CoViD-19, can be described through a modified version of the susceptible-infected-recovered (SIR) model with time-dependent contact ...

R (t), the effective reproductive number, is an important parameter in this model as it reflects the change in R0 (the basic reproduction number) with time and mitigation strategies.

Scientists used a SEIR model and a Bayesian inference framework to estimate the basic reproduction number of COVID-19 across Africa.