Explainer: How the Ministry of Health counts new, probable cases

Dr Ashley Bloomfield has been revealing the new number of confirmed and probable cases in New Zealand each day through the COVID-19 pandemic.
Dr Ashley Bloomfield has been revealing the new number of confirmed and probable cases in New Zealand each day through the COVID-19 pandemic. Photo credit: Getty

It's the must-watch press conference - Director-General of Health Dr Ashley Bloomfield standing at the podium to tell the country how many new cases there are each day.

However the number everyone is waiting to hear doesn't reflect the number of how many tests have come back positive each day.

On April 12, New Zealand had 18 new or probable cases.

But when you add them up on the Ministry of Health website there are 25 new or probable cases.

Explainer: How the Ministry of Health counts new, probable cases
Photo credit: Ministry of Health website

Three DHBs had either had a case become "suspected" or a negative result come back for a probable COVID-19 case.

Which means the increase of new cases on our country's total only goes up by 18.

Same too, yesterday.

Dr Bloomfield said "the increase was 17". But tally them up and there were 19. However, Hutt Valley DHB lost two cases.

Explainer: How the Ministry of Health counts new, probable cases
Photo credit: Ministry of Health website

The Ministry of Health says "the 'change in the last 24 hours' column shows the net increase/decrease in the total probable and confirmed cases".

If there is a negative number in this column, then the number of new probable cases is less than the number of probable cases dropping off the total due to a change in status.

"For example if we report 20 new cases total, we may have originally considered to have had 22 new cases but two probable cases were removed due to them being updated to not a case," a spokesperson told Newshub.

On Wednesday April 15 the Ministry of Health confirmed New Zealand had 20 new cases of COVID-19, six of the cases are confirmed while 14 are probable.