Flattening the COVID-19 curve…

Practically every time Dr. Fauci — the CDC’s undisputed truth teller — speaks, he references “flattening the curve”.

Graphically, here’s what he talking about…

Source: The Lancet

Let’s drill down on the chart…


The chart is simply an application of classical “diffusion theory” — oft used to explain the adoption of new innovations and the spread of communicable diseases.

Focusing on the red “base case” line above, the curve is mathematically driven by 3 main factors: (1) the number of “starter” cases (2) the replication rate, and (3) the length of the replication cycle.

Let’s take a simple example … assume that we start with one case, that each case replicates (i.e. “infects”)  2 additional cases and that it takes 1 day for the virus to replicate.

Given those parameters, we’d start with 1 case … have 3 cases in the 2nd day (the original case plus the 2 replications) … 7 cases in the 3rd day(the original case plus its 2 replications plus 4 replications off the 1st days replication) … and so on.

The big takeaway is displayed below: the cumulative number of cases grows very rapidly … in mathspeak: “exponentially” based on the replication rate.


Eventually you run out of people susceptible to infection and the curve peaks. Again, see the red line above.


So, how to “flatten the curve”?

Answer: Focus on the curve-driving factors:

1. Impede the number of starter cases, e.g. by banning travelers from existing hot spots.

2. Reduce the replication rate, e.g. by strictly quarantining known contagious patients … and by “social distancing” — keeping uninfected people out-of-reach of non-quarantined contagious people.

By doing the above, the contagion isn’t eliminated … but its diffusion curve is flattened: the peak is lowered and delayed, i.e. time-shifted until later … and the whole curve is spread over a longer time period (i.e. its effect gets “diffused”). See the green line above.


Even though the total contagion isn’t reduced, fattening the curve has 3 major benefits:

1. It reduces the immediate demand on healthcare facilities … spreading it out over a longer time frame.

2. It buys time to produce short-supply medical equipment, meds and supplies

3.  Maybe, it even buys enough time for virus-treating therapies to be developed and launched.


For an excellent scientific recap, see:

How will country-based mitigation measures influence the course of the COVID-19 epidemic?


Follow on Twitter @KenHoma

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One Response to “Flattening the COVID-19 curve…”

  1. Deepak Gupta Says:

    Glad to see you and PTOUS no longer is in denial mode on severity of COVID 19 at least. It is real problem and not a Fake news or Dem Hoax.

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