COVID-19 Worldwide in 2020~ Computation of r and Re in Excel

In 2020 we looked at Case numbers of COVID-19 worldwide using data up to 6 August 2020. Data by country/region daily was in 28,800 rows in an Excel 2010 spreadsheet.

We used initially this methodology to estimate daily increases, r, over five-day intervals:

C and r are the case numbers and value for r (daily increase over a five-day period) on day d.

We now estimate Ro this year, using the formula

Re = r ^ 2.5

where Re is the effective reproduction rate.

See:

COVID-19 Worldwide in 2020~ How many people may one person infect on average? What can we expect when Re = r^2.5?

We did look at a weighted average (0.25 and 0.75) or (0.75 and 0.25) but retained using a consecutive two-day (non-weighted) average.

We make the process clearer by looking at the United States and China.

Above we calculate

5501/641 = 8.58190

8.58190^(1/5) = 1.53715

and

(1.53715 + 1.45938)/2 = 1.49827

The maximum value obtained for r* is the value we use to estimate r for each country/region worldwide.

We note that had we not averaged r* over two days, 1.53715 (alone above) would have produced an estimate for Re of

1.53715^2.5 ~ 2.93

This means instead of adding on 0.1 we may now need to consider adding on at least 0.2 (an extra 0.1) to our Re estimate, to estimate Ro worldwide. See the last highlighted column in the last image below.

e.g. Instead of 2.9, Ro may be 3.0 for China.

We do the same calculations for the United States:

We obtain worldwide:

For all countries/regions see this PDF:

COVIDWorldAllCasesCPMRo

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