We revisit data for the spread of COVID-19 in early 2020.
We see in China that a daily increase close to r~ 1.5 fits the case data well from 23 Jan to 28 January 2020.
We have seen in New Zealand that a daily increase close to r~ 1.4 fits the case data well from 16 to 26 March 2020.
For definitions look at the bottom of this post.
retrieved 7 May 2020 from
Note: Case numbers have been updated from the values in the above table.
We conclude that r ~ 1.51 will provide a good value to calculate Ro using China case numbers.
From the table below we see that for r = 1.51, Ro ~ 7.8.
In New Zealand we have already seen that r = SQRT(2) works well and gives R0 ~ 6.
We conclude that in early 2020 Ro is likely to be in the range 6 to 7.8.
The above graph was obtained from this article: taaa021 (Click to view PDF):
The reproductive number of COVID-19 is higher compared to SARS coronavirus
published 13 February 2020, obtained from here:
(Journal of Travel Medicine, Volume 27, Issue 2, March 2020)
We have already estimated Ro for the Delta variant to be between 9 and 12.
This may suggest that Ro for the Alpha variant may be centred around 8.4; maybe in an overlapping range of 7.4 to 9.4.
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).