at the start</em> of a COVID-19 outbreak, the virus jumps from an <icon i></icon> to an <icon s></icon> every 4 days, <em>on average</em>.<sup id="fnref2"><a href="#fn2" rel="footnote">2</a></sup> (remember, there&#39;s a lot of variation)</p>

	<p>If we simulate &quot;double every 4 days&quot; <em>and nothing else</em>, on a population starting with just 0.001% <span class="nowrap"><icon i></icon>,</span> what happens? </p>

	<p><strong>Click &quot;Start&quot; to play the simulation! You can re-play it lat