SEIR

A SEIR model is a compartmental model used in infectious disease epidemiology that divides a population into four groups—susceptible (S), exposed (E), infectious (I), and recovered (R)—to describe how a disease spreads over time. Individuals move from susceptible to exposed after contact with an infectious person, then to infectious after an incubation period, and finally to recovered (or removed), allowing the model to capture diseases with a latent (non-infectious) phase.