On Monday 23 March, Prime Minister Jacinda Ardern said without Level 4 measures, medical modelling showed Covid-19 would kill tens of thousands of New Zealanders. Genevieve O'Halloran looks at what those numbers really mean.

“The worst-case scenario is simply intolerable. It would represent the greatest loss of New Zealanders’ lives in our history and I will not take that chance.” That’s how Prime Minister Jacinda Ardern described the need for lockdown on Monday.

Professor Michael Baker, an epidemiologist and public health expert from the University of Otago welcomed the lockdown. Baker said while new cases of Covid-19 were rising exponentially in New Zealand, the shutdown meant "we can interrupt that curve”. 

Getting ahead of the curve, he said, would take at least two weeks. Currently incubating cases are yet to be identified and it will take several weeks after lockdown takes effect for chains of transmission to be broken.  

“We would expect the curve to start to go down or flatten out in two to three weeks.”

But talking about curves is all very well. What exactly, in human terms, do those data points represent? 

The numbers are a moveable feast. The virus is much more likely to be fatal for those aged over 70, meaning countries with older populations are more affected. The amount of tests carried out varies wildly between nations. 

Criteria for testing also varies between countries. The broader the testing regime – testing even those who display no symptoms – the lower the mortality rate. Testing that captures milder cases (who are more likely to recover) decreases the total mortality rate.  

But there is enough to form a picture of what modelling might have told the Prime Minister. 

The World Health Organisation’s latest estimate of the Coronavirus mortality rate, released in early March, is that it kills 3.4% of those infected. 

It’s hard to know how many people would be infected, but we can look to other countries for their estimates. At the high end, England's chief medical officer estimated that up to 80% of their population could be infected. 

If 80% of New Zealand’s population were to be infected, that mortality rate represents 130,000 dead New Zealanders – 2.7% of New Zealand’s total population. That’s about the population of Dunedin.

With 20% of the population infected, a 3.4% mortality rate equates to a death toll of 32,000 – that is, 0.67% of New Zealand’s population. 

By comparison, over 11,000 New Zealanders died in military action in World War Two –  0.73% of New Zealand’s then-population.

But the death toll is varying country by country. In Italy, the death toll is running at 12.6% of those infected, with 54,030 confirmed cases and 6820 dead. In Singapore, with 355 confirmed cases and 2 dead, the mortality rate is 0.56%. 

Why does Singapore have such a low death rate?

Most New Zealanders would feel uneasy living under Singapore’s benignly authoritarian system of government. But viruses have no respect for liberal democracies, and Singapore’s clinical efficiency has proved to be a match for Covid-19. Its pandemic preparedness was further improved by the SARs crisis of 2003, and H1N1 in 2009.

Surveillance services and the police have helped Singapore’s government identify close contacts of confirmed cases. Close contacts are then quarantined. Details of confirmed cases are published swiftly online, allowing others to be tested, treated and quarantined. Transit travellers have now been banned, and returning residents will have to quarantine for 14 days at home or face a maximum fine of S$10,000, and up to six months in jail. Testing is widespread. As of March 20, Singapore had carried out 38,000 tests – or about 6,800 per million of population. 

As of today, New Zealand has carried out 9780 tests; 490 tests per million of population. 

Why has Italy’s experience been so grim? 

In contrast, Italy, home of la dolce vita, the deaths keep coming. The obituary notices in the local papers have ballooned, pages upon pages of Nonnas. 

Italy’s aging population has been cited as one reason for its high death rate, and its congregational culture – Sunday lunch a la familia, the kisses on the cheeks, the espresso at the bar – all considered as contributing factors.  

The speed of Italy’s response has been criticised, but it wasn’t unduly slow. Affected regions of Lombardy were locked down on 21 February, within days of the first deaths. The rest of the country was locked down on 8 March, when confirmed cases had spiked to over 5800, with 233 dead. 

So how will New Zealand fare?  

We will not be Singapore. We have no practice in pandemics, and we have no tradition of obediently following government orders. So far, we have sought to manage this virus through requests rather than directives. 

But nor are we Italy. Our cases are increasing, but we have taken radical action before people have died. We have had time to prepare. Our cities are quiet by international standards. Is this enough for us to avert Italy’s fate?

There will be no more happy, noisy crowds dining cheek-by-jowl in our restaurants any time soon. Coronavirus, which in late February had seemed so remote – a faceless evil happening to other people far away – has arrived on our doorstep.

We are standing at the foot of a tsunami, and all we can do is wait, and hold the line. There’s no number 8 wire ingenuity required, no atom-splitting or Everest climbing. Just wait, at home, and wash our hands.