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COVID-19 in NZ in Early 2020~ Does Re = 5.8 and Ro = 6?

Posted by AlanGraceNZ on

Two years ago today on 7 July 2021 we looked back at our analysis of COVID-19 in NZ in early 2020 as the breakout occurred in New Zealand. In New Zealand we discovered than a daily increase of r = 1.4 fitted the New Zealand cases numbers well.

First look at our 7 July 2021 post for definitions:

COVID Odyssey: Winter Windup 5 ~ Conclusions for NZ in 2020 ~ Back to the past: Re = 5.8 and Ro = 6

Warning:

In this post below we have used r^5 to estimate Re. We have decided this may not be a good idea. A link to an updated post is here:

Update 2: COVID-19 in NZ in Early 2020~ Does Re = 5.8 and Ro = 6?

Today we look at whether our results for Ro and Re are achievable.

We assume that each infected person spreads the disease for two 5-day cycles.

Also see:

https://abcnews.go.com/Health/r0-covid-19-virus-key-metric-opening-plans/story?id=70868997

“When will it be over?”: An introduction to viral reproduction numbers, R0 and Re 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7751056/

We explore seeing if Re = 5.8 is achievable matching the NZ case numbers and obtain:

NZCOVID1

This PDF may be easier to read:

COVIDNZ1

Column C contains the NZ cases numbers early in 2020.

Cloumn E contains the estimated case numbers with adjustment for the second 5-Day cycle in Columns G and H.

With this adjustment the data matches well the case numbers on Day 5 and Day 10.

We used Goal Seek in Excel to set cell H4 to zero by changing cell E3.

The table on the top right shows the potential increases in case numbers at the end of each cycle assuming no isolation or immunity. The population of New Zealand was just over 6 million. Of course people infected with COVID-19 would have natural immunity.

We also wanted to see if Ro = 6 was achievable so we calculated results again for Re = 6 using again r = 1.4 approximately. In reality since 1.4 x 1.4 = 1.96, since this is close to 2, this suggests that r = SQRT(2) may be appropriate for estimating Ro.

We obtained this the results below:

NZCOVID2

Also see this PDF:

COVIDN2

We also saw that Re = 6.46 was also possible:

NZCOVID3

Also see the PDF version:

COVIDNZ3

This matches the case numbers exactly on Day 5 and day 10.

We conclude that Ro = 6.04 is possible.

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