virophysics

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# COVID-19: A closer look

Hi there! Curious about the math behind infection spread? I've posted a quick intro below.

### Counts of new cases and deaths each day

C stands for Cases, and D for Deaths. The dots are the actual data, the (not always visible) red line is the smoothed data (Gaussian kernel, $$\sigma$$=4.5 days, applied to the log of the daily case count), the blue line is a set of linear segments identifying periods with the same reproductive numbers, likely coinciding with the start/end of public health measures (# and location of inflection points is that of highest likelihood based on BIC). The black and blue lines over the daily death counts are actually the red and blue lines for the daily case counts shifted by some # of days and multiplied by some percentage, both indicated in the legend. These #s suggest Japan (12 days between Case identified to Death, 5% of Cases result in Death) is doing better than France (7 days Case to Death, 18% of Cases result in Death), because France takes about 5 days more to test and report infected individuals as cases, and identifies 3-4 times fewer infected individuals as cases.