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 2

The fourth in our new series of charts, graphics and data visualisations by Chris McDowall, covering the Covid-19 epidemic within New Zealand. We’ll publish the latest set each day on The Spinoff.

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

Information about confirmed and probable cases of Covid-19 in New Zealand is changing rapidly. These posts collate the most recent statistics and presents 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. The Spinoff will release a new version of these data visualisations each day in the immediate aftermath of the Ministry of Health updates. They will evolve and refine over the coming days and weeks.

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: the charts are not supported within the app yet. Please click here to launch in a separate browser window.

This afternoon’s Ministry of Health figures report that the number of active Covid-19 cases stands at 797 (723 confirmed cases and 76 probable). Ninety-two people have recovered, an increase of 10 over the last 24 hours. The ministry offered the clarification that “a person is defined as recovered if they have been without symptoms for 48 hours.”

The ministry also reported that they averaged 1,835 Covid-19 lab tests per day during the week ending April 1. A total of 26,015 lab tests have been conducted to date.

This symbol map shows confirmed and probable Covid-19 cases arranged by district health board. Waikato DHB increased by 26 cases overnight, from 91 yesterday to 117 today. Hover of the dots to see more detailed data.

The ministry is now only publicly reporting clusters with 10 or more cases. Note that all clusters are being investigated by public health officials, irrespective of their size. The ministry also reduced the level of detail in the name of each cluster. For example, the Marist School cluster is now simply identified as “school”.

The number of probable and confirmed cases in the three largest clusters increased again overnight. The largest increase related to a Southland event, which recorded 12 new cases in the last 24 hours.

This bar chart displays confirmed and probable cases by the “date of report”. There are complexities behind that simple phrase. It is unclear to me precisely what “date of report” refers to.

  • When a case first enters the health system?
  • When the person first takes a Covid-19 test?
  • When the test results arrive back?
  • Some other event?

I have sought clarification from the Ministry of Health, who are understandably very busy. I will report back when I get a response.

At the time of writing, 53.8% of active cases are female (429) and 45.3% of cases are male (361). A further 0.9% of cases are unspecified (7). This chart shows how female and male cases breakdown since March 12. Note the switch that occurs around March 24 when female cases start consistently outnumbering male cases on every daily count.

Please forgive any clumsiness in my use of the terms “female” and “male”. These are the categories the ministry uses and I try to minimise distorting the official figures in these columns.

The total cases by age group chart has the same basic shape as the last few days. There are cases recorded for every age group, with a strong protrusion in the 20 to 29-year-old group.

This final chart comes from the GNS Science GeoNet seismometer network. A seismometer is an instrument that detects and records ground motions. GNS uses them to listen for earthquakes. The urban sensors also pick up the low-level rumbling of vehicles moving about the city. Each ‘bump’ in the image above represent a day of activity — the city wakes up, people move around, the city returns to a low-level rumbling. Note how the daily ‘bumps’ decrease as we move through the yellow alert levels.

“As the country started to #StayHomeNZ to help eliminate the spread of COVID-19 we recorded a significant decrease in noise about Auckland city by our seismometers. In the attached plot we are looking at the signal from the borehole sensor at Herne Bay in the city, this borehole is our deepest at 380m deep. In the RSAM plot for the last month you can see the normal weekly cycle of the city, busy Monday to Friday, a slowdown in the afternoon on Saturday and quietest on Sunday. And last week we could see the city start to slow down on Tuesday-Wednesday when New Zealand went to COVID-19 Alert Level 4. It has been at typical weekend levels since then.” – GNS Science GeoNet

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