COVID-19 NZ: Could NZ have had over 4,000 cases early in April?

We look to see how many cases New Zealand may have had if the county had not gone into Lockdown Level 4 on Wednesday 25 March at 11.59 pm.

We continue to look at the model used in the two previous posts.

The model is very simplistic.


We note that New Zealand had a total of 368 cases on 27 March, close to the figure in the table below on 23 March.
i.e. If our start date was four days later, the total would have matched the daily total on 27 March.


We note that had New Zealand not gone into Lockdown Level 4,  the model estimates a total of 962 cases on 29 March and 2500 cases on 4 April (add on 4 days if you wish to match the 368 figure).

Adding on 4 days gives the following table:
(we will ignore [the dates in] this table in the discussion below)


New Zealand could have had over 2,500 cases 12 Days after the total was 368.

Six days later the figure reached over 6,500 in the model.

New Zealand only reached 1500 (1503) cases yesterday.

However the above model does not match the actual totals (last two columns) well:


A 5-day cycle works better:




For an exact match (514) above on 29 March, use Re = 2.86368569122729
(a good exercise in using goal seek in Excel).

To compare the 6-day and 5-day models, we need to consider a 30-day period (5 x 6 = 6 x 5).

The above models start with 5 cases. We use the dates in the tables above and consider a 30-day period.

For the original 6-day model (28 Feb – 29 March) we have 962 cases (one extra cycle).

For the above 5-day model (9 March – 8 April) we have a total of almost 4,300 cases (two extra cycles).

On 8 April, the total number of cases could have exceeded 4,000 cases or close to 1,500 on 3 April if New Zealand had delayed a week before going into Lockdown Level 4.

Below are the actual total number of cases for New Zealand from 23 March to 8 April:
(Date, Day number, Total cases)


My other COVID-19 posts can be found here:

Data for my posts can be found at:

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