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Prevalence Bathtub: Incidence × Duration

Interactive 3D stock-and-flow model of disease prevalence: new cases flow into a population pool at the incidence rate, sit there for the illness duration, then exit as recoveries or deaths — watch the steady-state prevalence converge to Incidence × Duration.

Medicine & Biophysics3DModerate60 FPS📱 Mobile-adapted⇄ 2D version

Epidemiologists separate two very different questions: how fast is a disease being caught (incidence) and how many people currently have it (prevalence). This simulator renders that relationship as a physical tank — a real 3D "prevalence pool" that new cases fall into at the incidence rate, drift inside for roughly the illness duration, and then leave through one of two chutes: recovery or death, split by the case-fatality proportion. Because each case's residence time is drawn from a memoryless exponential distribution (the same simplifying assumption compartmental SIR/SEIR models use for recovery), the pool's population settles toward the classic steady-state identity Prevalence ≈ Incidence × Duration, visible live as the gap between the current headcount and the dashed target closes.

⚙ Under the hood

An interactive 3D stock-and-flow model of disease prevalence: new cases flow into a population pool at the incidence rate, sit there for the illness duration, then exit as recoveries or deaths, letting you watch prevalence converge to the steady-state Incidence × Duration identity.

epidemiologyprevalenceincidencepublic healthbiostatisticscase-fatality

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install