Open Access
Article
Near-Exact Analytical Solution of the SIR-Model for the Precise Temporal Dynamics of Epidemics
Reinhard Schlickeiser1, 2, *
Martin Kröger3, 4, *
Author Information
Submitted: 6 Nov 2024 | Revised: 28 Nov 2024 | Accepted: 11 Dec 2024 | Published: 26 Dec 2024

Abstract

A near-exact analytical solution of the statistical Susceptible-Infectious-Recovered (SIR) epidemics model for a constant ratio k0 of infection to recovery rates is derived. The derived solution is not of inverse form as the known solutions in the literature but expresses rather directly the three compartmental fractions S(τ), I(τ) and R(τ) and thus the rate of new infections j(τ) = S(τ)I(τ) in terms of the single function U(τ) and the reduced time τ (the time-integrated infection rate), involving the principal and non-principal branches of Lambert’s function. Exact analytical formulas for the peak time and the maximum fraction of I(τ) are obtained proving that the rate of new infections peaks before the fraction of infected persons. Our analysis is not entirely analytically exact because the reduced time dependence of the function U(τ) obeying a nonlinear integro-differential equation is only obtained approximately by expanding a double-exponential function to first-order at small reduced times, and employing an accurate simple approximation of the principal Lambert function at large times, respectively.

References

Share this article:
Graphical Abstract
How to Cite
Schlickeiser, R., & Kröger, M. (2025). Near-Exact Analytical Solution of the SIR-Model for the Precise Temporal Dynamics of Epidemics. Applied Statistical Analysis and Computing, 1(1), 100002. https://www.sciltp.com/journals/asac/articles/2504000524
RIS
BibTex
Copyright & License
article copyright Image
Copyright (c) 2024 by the authors.

This work is licensed under a This work is licensed under a Creative Commons Attribution 4.0 International License.

scilight logo

About Scilight

Contact Us

Suite 4002 Level 4, 447 Collins Street, Melbourne, Victoria 3000, Australia
General Inquiries: info@sciltp.com
© 2025 Scilight Press Pty Ltd All rights reserved.