# SEIR Model **Entity class:** Compartmental epidemic model **Domain:** Mathematical epidemiology / diffusion **Maturity:** Developed ## Definition The **SEIR model** extends SIR by adding an **exposed (E)** or latent compartment between susceptibility and infectiousness. It is useful when acquisition and onward transmission are separated by an incubation period. In radicalization research, the exposed state may represent contact with a narrative or network before observable recruitment or mobilization. That translation is provisional: online viewing, persuasion, ideological commitment, operational capability, and violence are distinct, and the latent period is rarely observed as cleanly as an incubation period in infectious disease. ## Relationships - **extends:** [[wiki/SIR Model|SIR Model]]. - **member of:** [[wiki/Epidemic Model|Epidemic Model]]. - **network alternative:** [[wiki/Complex Contagion|Complex Contagion]]. - **operational comparison:** [[wiki/Contact Tracing|Contact Tracing]]. ## Sources / Provenance - [National Library of Medicine — Epidemiological modeling of terrorist networks](https://pmc.ncbi.nlm.nih.gov/articles/PMC7299159/)