COVID-19: Proof that 5 April was NZ COVID-19 midpoint. NZ should not come out of Level 4 Lockdown for 4 extra weeks!

The graph below is visual “proof” that New Zealand case numbers reached the midpoint on 5 April!

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Update: For my conclusions at the Lockdown midpoint (posted on 9 April), please see:
https://aaamazingphoenix.wordpress.com/2020/04/09/nz-covid-19-conclusions-at-initial-lockdown-midpoint-nz-should-stay-at-level-4-lockdown-for-an-extra-4-weeks/
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We conclude that Level 4 Lockdown should continue until at least 14 May even if the peak/midpoint may be earlier than 5 April (Day 38). We will not know this for maybe at least a few more days.

We should expect to have Level 4 Lockdown for at least an extra four more weeks beyond the initial four weeks to ensure there are no further cases.

In my previous post we looked at New Zealand case numbers. See:
https://aaamazingphoenix.wordpress.com/2020/04/06/covid-19-nz-how-many-cases-and-deaths-may-we-expect/

Yesterday’s case numbers and the graph below suggest a midpoint on 5 April.

Here is the graph including today’s data:

Note: the equation for the straight line was created on 2 April (Day 35) or earlier by me using linear least squares in Excel. See:
https://aaamazingphoenix.wordpress.com/2020/04/02/covid-19-nz-cases-currently-linear/

At first I was puzzled. Why, when consistently the real number of cases was close to the straight line, was it for two days clearly above the graph?

The most likely answer to this was that the midpoint was actually on 5 April and the number of cases was now trending downward.

This may suggest that the bar graph may be trimodal (if that’s a word). i.e. the bar graph may soon have three peaks depending on how symmetric the bar graph appears later.

Day 38 (5 April) and 39 (6 April) and had 1,039 and 1,106 cases respectively. The sum of these (2,145), suggests the total number of cases (excluding a long tail). See my posts for China deaths to find out why we have done this.

Once again we add on 10% to allow for the tail (at least partially).

This gives 2,359 cases total which we round to 2,400.

In the last post we gave a range from 1,500 to 3,000 for the number of cases.

The mid-value for this range is 2,250. Halfway between 2,145 and 2,359 is 2,252!

Below is the bar graph including today:

Looking at the bar graph you will see that a peak occurred on 5 April. While it is tempting to use Day 37 and 38 for the calculation it is safer to use Day 38 and Day 39.

From the first graph, using Day 37 and Day 38 still gives 1,989 (=950+1039) cases. Adding on 10% gives 2,187 case, say 2,200 cases.

We also note that 2 x 1039 = 2078. Adding 10% gives 2,285 (say 2,300) cases.

We now have a range of 2,200 – 2,400 cases. It is safer to assume 2400 cases total.

We note that our original range of 1,350 to 2,700 cases (see previous post) gives a mid-value of 2,025 cases, reasonably close to 1,989.

Using Day 38 and 39 even without a long tail, cases will continue until at least Day 77 (=38 + 39). i.e. 14 May.

Extra time may be needed to allow for a long tail.

China is still getting new cases and deaths about one month after its tail started to have very low numbers.

We conclude that Level 4 Lockdown should continue until at least 14 May even if the peak/midpoint may be earlier than Day 38. We will not know this for maybe at least a few more days.

This means to be safe Level 4 Lockdown should be extended for at least three extra weeks after the initial 4 weeks.

The Level 4 Lockdown should continue longer if there is a long tail. i.e. There are still new cases.

We should therefore expect to have Level 4 Lockdown for at least an extra four more weeks to ensure there are no further cases.

My other COVID-19 posts can be found here:
https://aaamazingphoenix.wordpress.com/tag/coronavirus/

Data for my posts can be found at:
https://www.worldometers.info/coronavirus/
https://en.wikipedia.org/wiki/2020_coronavirus_pandemic_in_New_Zealand

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