The SEIR model adds an Exposed (latent) compartment between Susceptible and Infectious.
Disease States
- S: Susceptible - can become infected
- E: Exposed - infected but not yet infectious
- I: Infectious - can transmit disease
- R: Recovered - immune
Key Differences from SIR
- Delayed epidemic peak
- Lower, broader infection curve
- More realistic for diseases with incubation periods
- Examples: COVID-19, measles, chickenpox
Parameters
σ (sigma) = 1/incubation period. Higher σ means shorter latent period, approaching SIR dynamics.