Have we knocked the bastard off?
New Zealand finally reached a significant milestone on Monday, with the last remaining known person with an active case of Covid-19 fully recovering from the virus.
When New Zealand went into lockdown on March 25 modelling showed there could be many thousands of cases before the tide started to turn.
In the end New Zealand’s outbreak only reached 1504 confirmed or probable cases. Twenty-two of those who contracted the virus would die. The number of active cases peaked at 929 on April 6 in the middle of the Alert Level 4 lockdown. But with the lockdown taking effect, that number began a steady decline.
On April 25 the number of people recovered from the virus, outnumbered the number of active cases for the first time. Just over a month later on May 29, New Zealand was down to one remaining active case. A person is considered to have recovered if they display no symptoms for 48 hours. Many other countries have managed to contain the virus. Iceland (population 364,000) is on the verge of elimination. As of Monday, Iceland has two active cases (based on most recent data from Sunday). Iceland invested in massive testing but took a more relaxed approach to social isolation and movement restrictions than New Zealand.
The divergent approaches were quantified by Oxford University’s stringency index. On a 0 to 100 scale, New Zealand scored a whopping 96.3 at the peak of its lockdown. It was the only nation among World Bank’s highincome economies to go above the threshold of 90. Since the easing of restrictions, New Zealand’s stringency index fell to just 36.1.
Iceland, where cafes and restaurants stayed open throughout the epidemic, has maintained a 53.7 stringency score since mid-March.
Clusters
New Zealand’s outbreak was dominated by a series of clusters of 10 or more cases, which mostly originated in ‘superspreader’ events, such as weddings, pubs and a school.
There were also several outbreaks within rest homes, including the Rosewood Rest Home in Christchurch, which resulted in most of New Zealand’s Covid-19-related deaths.
As the outbreak progressed, new cases were increasingly linked to these clusters. In addition to decreasing numbers of new cases, this was a sign that Covid-19 was coming under control.
The clusters now account for 41 per cent of all known probable and confirmed cases. Since the start of May the number of new cases linked to a known cluster is 446, out of 507 new cases total in that time.
Testing
New Zealand has the fifth highest rate of testing per capita in the world. Almost 5 per cent of New Zealanders have been tested. Only Israel, Estonia, Italy and Russia have reported more tests per capita.
As testing ramped up and cases dropped off, the test positivity rate (ratio of positive results to tests) dropped away.
However, as the outbreak has come under control the number of people getting tested has declined. The sevenday average number of tests conducted peaked at 6000 on May 13, but have tailed off ever since.
The need for vigilance
New Zealand has seemingly eliminated its Covid-19 outbreak. But experts warn there is still a chance of further outbreaks.
Modelling by Te Pu¯ naha Matatini suggests there is a 5 per cent chance of undetected cases in New Zealand. And that even if the virus has been completely eliminated there remains a risk of new cases being imported and starting an outbreak.
New Zealand moved to level 1 at midnight yesterday, essentially returning to normal with the exception of border controls. We need to ensure contact tracing systems are good enough to contain an outbreak caused by a superspreader in a crowded space.
NZ: 5 million v Covid 19: 0