Ro is the number of people that on average one person with COVID-19 may infect.
Note: The formula in this post has been updated. See:
Early in 2020 we arrived at the following table for calculating Ro:
Before the above table we used this formula and table:
Which gives the more realistic results?
We know from our analysis that a 5-day cycle produces the best results.
We assume that a person with COVID-19 becomes symptomatic (shows symptoms) after one cycle (5 days) and may be infectious for 2 or maybe 3 cycles.
We also now that a person may become infectious days before symptoms appear.
In our simulations we initially built in an extra day incubation period but decided to later not have an extra incubation day.
The first table shows the results for no incubation day.
The second table shows the results with the extra day incubation period,
Essentially the first table shows results when a person is infectious 24 hours after infection (the next day).
The second table shows results when a person is infectious 48 hours after infection (two day’s later).
On reflection the (original) scenario/second table appears more realistic.
Our analysis shows in new Zealand the daily rate of increase is around r = 1.4.
To convert between the tables multiply or divide Ro by r.
We may assume that this is likely (without isolation/quarantine) to increase to r = SQRT(2).
We conclude that on average the second table is best.
This means that one person with COVID-19 early in 2020 is likely to infect around 6 other people on average when n = 10 days. i.e. Re = 5.8 and Ro = 6 is likely.
What do you think?
By definition we let:
- r denote the effective Reproduction rate of COVID-19 for one day
- Ro (R0; R-Zero; R-Nought) denote the Reproduction number for COVID-19 without any quarantine or isolation
- Re denote the effective Reproduction number for COVID-19
(Re assumes isolation/quarantine is happening)
- a case be defined as a person diagnosed as having COVID-19
Note that Ro and Re are numbers (not rates), the number of people one person with COVID-19 may infect on average without quarantine or isolation (Ro) and with quarantine or isolation (Re).
Also see my previous posts: