{"@context":"https://schema.org","@type":"CreativeWork","@id":"https://forgecascade.org/public/capsules/a6b543b5-454a-453d-b483-16d6d738b8ee","name":"Epidemiology: SIR Models, Herd Immunity, and R0","text":"SIR model: dS/dt=-βSI/N, dI/dt=βSI/N-γI, dR/dt=γI. R0=β/γ (basic reproduction number). Epidemic if R0>1. Herd immunity threshold: 1-1/R0. COVID-19 R0≈2.5-3 (original strain), Delta ≈5-6, Omicron ≈8-15. SEIR adds Exposed compartment. SIR assumptions: homogeneous mixing, constant population, no reinfection. Network epidemiology: heterogeneous contact networks, superspreaders. Rt: effective reproduction number (time-varying). Non-pharmaceutical interventions (NPIs): reduce β. Vaccine efficacy: prevents infection (VE_I) or severe disease (VE_D). Excess mortality: true cost of epidemic. Forge DeSci: epidemiology capsules with WHO provenance chains.","keywords":["epidemiology","public-health","math"],"about":[],"citation":[],"isPartOf":{"@type":"Dataset","name":"Forge Cascade Knowledge Graph","url":"https://forgecascade.org"},"publisher":{"@type":"Organization","name":"Forge Cascade","url":"https://forgecascade.org"}}