We consider how much greater Ro is than Re.
We look at the following table:
For definitions see:
In New Zealand both r = SQRT(2) and r = 1.429 provide good estimates for the total number of cases from 21 to 25 August 2021. See:
These values for r correspond to Re = 6.047 and Re = 6.308.
This gives us the above range in New Zealand for the delta variant under Lockdown Level 4.
We obtain Ro in New Zealand in the 2021 Lockdown level 4 could have been as high as 6.57.
In New Zealand we have seen r =1.4 works well for a daily growth factor.
1.4 x 1.4 = 1.96.
This means that cans that we can expect case numbers to almost potentially double every two days.
Case numbers could double every two days if r = SQRT(2).
We use this value to estimate Ro using our formula:
We use the factor F = SQRT(2)/1.4 to estimate Ro for other values of Re.
This provides us with the estimates in the table at the top of this post.
We have also seen in China and the USA in early 2020 r is close to 1.5.
This provides us with Ro = 7.931.
This gives us a range for Ro for the original COVID-19 outbreak in 2020 of 5 to 8.
Recall that for UK in early 2020 we estimate r > 1.35 and hence Ro is at least 5. See:
We obtain the table below:
The PDF version may be easier to read:
Ro may be far greater than Re than we have indicated.
The factor and values of r we have used to calculate Ro provide a minimal estimate just over 1% higher than high values of r we have used to estimate Re.
The effect of the increase can be seen here:
Higher factors may increase the range significantly for our estimates for Ro.