Epidemic Forecast Follies

TL;DR

This paper presents a simple multiplicative model for epidemic dynamics that captures the effects of public health measures and explains the variability and fluctuations in epidemic outcomes and trajectories.

Contribution

It introduces a minimalist multiplicative model that accounts for public health interventions and explains the diverse and fluctuating epidemic behaviors.

Findings

Epidemic outcomes vary significantly even with identical starting points.

Epidemic trajectories are characterized by strong fluctuations.

Different epidemic instances can have disparate outcomes despite similar initial conditions.

Abstract

We introduce a simple multiplicative model to describe the temporal behavior and the ultimate outcome of an epidemic. Our model accounts, in a minimalist way, for the competing influences of imposing public-health restrictions when the epidemic is severe, and relaxing restrictions when the epidemic is waning. Our primary results are that different instances of an epidemic with identical starting points have disparate outcomes and each epidemic temporal history is strongly fluctuating.