Director of health Ashley Bloomfield, who, on most days, reads the numbers that will define how the rest of this year plays out (Illustration: Simon Chesterman)

Covid-19: New Zealand cases mapped and charted, April 8

The latest in our new series of charts, graphics and data visualisations by Chris McDowall.

This work is entirely funded by the generosity of The Spinoff Members

These posts collate the most recent statistics and present them as charts and maps. The Ministry of Health typically publishes data updates in the early afternoon, which describe the situation at 9am on the day of release. These data visualisations are interactive – use your mouse or thumb to hover over each graph for more detail.

Note for users of The Spinoff App: if the charts below are not appearing, please click here to launch in a separate browser window. An update is imminent!

This afternoon’s Ministry of Health figures report that the total number of confirmed and probable Covid-19 cases stands at 1,210 (969 confirmed and 241 probable). A total of 241 people have recovered, an increase of 65 since yesterday.

Yesterday 4,049 tests were processed. This is the highest number of tests processed in a single day. The ministry reported averaging 3,343 Covid-19 lab tests per day during the week ending April 7. A total of 46,875 lab tests have been conducted since March 9. There are 49,193 lab testing supplies in stock — an increase of 5,308 from 43,885 yesterday.

This chart compares active and recovered cases. Active cases are people who currently have the Covid-19 virus. Recovered cases are people who had the virus, but are at least 10 days since onset and have not exhibited any symptoms for 48 hours. Although the ministry does not supply the number of active cases, we can calculate it with the following formula:

ACTIVE = CONFIRMED/PROBABLE – (RECOVERED + DEATHS)

Today there was a slight increase in the number of active cases — from 918 active cases yesterday up to 927 this morning. This is a good reminder to please continue observing lockdown procedures. As the prime minister stated in today’s briefing, “Alert level four remains in place and there is absolutely no change to the rules.”

This chart shows the number of Covid-19 tests conducted each day. We have been receiving daily updates on this measure for a week or so, but now the ministry are releasing the data as a handy table.

There are a few things to note about this chart. The first value in the daily test count data is for March 8. To ensure that the time series charts in this post are easily comparable, I added empty values February 28 to March 7. It is possible that some testing occurred during this time but, given the low levels of testing even in mid-March, I consider this a reasonable tradeoff.

The second thing to observe is that the number of new cases is dropping as the daily test count rises. This is a positive sign. Even with more tests, there are fewer cases.

Finally, there is a version of this chart that plots the number of new cases against the number of tests conducted each day. I would love to make this chart but, to my eyes at least, there is ambiguity around exactly when a case gets counted. I am seeking clarification from the ministry of health on this. Until then I will refrain from making a chart I that I am uncertain about. The broad picture is clear enough.

The symbol map shows confirmed and probable Covid-19 cases arranged by district health board. Southern (195), Waitematā (169), Waikato (159) and Auckland (155) remain the four district health boards with the largest number of active cases.

There are still 12 significant clusters under investigation. The largest increase is in the Marist school cluster, which grew from 77 to 84 cases overnight. The Bluff wedding cluster in Southland increased from 73 to 81 cases.

Two clusters got smaller as confirmed or probable cases were downgraded. Yesterday there were 35 cases connected with the Queenstown Hereford conference, today there are 33 cases. The Waikato rest home decreased from 14 to 13 cases. These two cases appear as slight anomalies on the chart as their “Under investigation yesterday” bar is longer than it would be if we plotted today’s total.

The time series chart showing confirmed and probable cases based on the “date of report” continues to look promising. Before getting too excited, please recall the active versus recovered chart and the fact that active cases rose slightly in the last 24 hours.

The age breakdown looks exhibits the familiar profile, with especially large counts for people in their 20s and 50s.



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