SIR Model on Chen Kai Bloghttps://www.chenk.top/en/tags/sir-model/Recent content in SIR Model on Chen Kai BlogHugoenWed, 07 Feb 2024 09:00:00 +0000Ordinary Differential Equations (14): Epidemic Models and Epidemiologyhttps://www.chenk.top/en/ode/14-epidemiology/Wed, 07 Feb 2024 09:00:00 +0000https://www.chenk.top/en/ode/14-epidemiology/<p><strong>In early 2020 the entire world watched a small system of ordinary differential equations decide policy.</strong> &ldquo;Flatten the curve&rdquo; was not a slogan; it was the intuition of a specific equation. <em>Herd immunity</em> was not a guess; it was the threshold <span class="math-inline">$1 - 1/R_0$</span> derived in a single line. The SIR model — four lines of math, written down in 1927 by Kermack and McKendrick — turned out to be precise enough to drive trillion-dollar decisions.</p>