Covid milestone probably a myth: health ministry
The PM danced, Ashley Bloomfield smiled broadly, praise flowed from around the world, but was ‘‘zero cases’’ actually true? Eugene Bingham investigates.
An achievement celebrated globally as a milestone in New Zealand’s fight against Covid-19 was almost certainly a myth.
Back in June, the country rejoiced in more than 24 days of zero cases, and a declaration there were no active cases in the country, an announcement which earned international acclaim, and caused Prime Minister Jacinda Ardern to do ‘‘a little dance’’ in celebration.
But the Ministry of Health confirmed to the Sunday Star-Times this week there were ‘‘probably’’ cases in the country that went undetected at the time.
And one of the scientists involved in building the models plotting the path of the virus, Dr Michael Plank, thinks it is ‘‘highly likely’’ positives were missed. How did this happen?
New Zealand did not start testing all arrivals until June 9, two months after setting up the Managed Isolation and Quarantine (MIQ) facilities. The 24 days finished on June 16, and, during that time, 5885 people landed in the country.
‘‘It’s important to remember that all of those 5885 arrivals did spend 14 days in managed isolation,’’ says Plank, a Canterbury University maths professor and principal investigator at Te Pu¯ naha Matatini.
‘‘That is what does most of the heavy lifting of reducing the risk of onward transmission in the community, because it’s unlikely – though not impossible – for people to still be infectious more than 14 days after infection.’’
Leading epidemiologist Dr Michael Baker discussed the missing cases with the Sunday Star-Times this week as part of a story about what he calls New Zealand’s
‘‘sluggish’’ response to the pandemic after initial decisiveness.
He had ‘‘breathed a sigh of relief’’ when testing was finally introduced.
‘‘And it was very notable that we had that long period where we didn’t seem to have any imported cases going into MIQ.’’
Baker says the possibility there really were zero cases was ‘‘extremely unlikely’’.
‘‘We graphed that period, and you can just go back and extrapolate back to the start and you can make some reasonable assumptions about how many people were infected.’’
Like Plank, Baker believes it’s likely cases were safely contained during the 14 days period.
But the nature of the virus – genomic testing shows that in only 20 per cent of the cases which arrived in the country before the borders were closed was anyone else infected – means it’s possible some cases left MIQ, but did not pass it on.
‘‘You might have five or 10 people who walked out into the community during that period who were still infectious, but didn’t infect anyone else.’’
For whatever reason – good luck, or the behaviour of the individuals – no-one else got sick.
‘‘It’s quite remarkable we didn’t get multiple failures around then.’’
Dr Des Gorman, a former associate dean of the Auckland Medical School, says: ‘‘The reason we didn’t have cases during that run is because we simply weren’t looking. And that’s when people like me were saying: ‘Look, community transmission is inevitable’.’’
The director of public health, Dr Caroline McElnay, says she’s ‘‘fairly confident that there were not people discharged from facilities after 14 days who were still infectious’’.
‘‘Were there people who were, during those 14 days, cases we didn’t know about? Probably, yes, because we weren’t testing.’’
Plank says the introduction of border testing was important. ‘‘This helps us isolate confirmed cases and therefore reduce the risk of them spreading the virus to other travellers or workers in MIQ, who could then carry it out into the community.’’
After the announcement on June 8 there were no active cases, New Zealand attracted global headlines.
The Director-General of Health, Dr Ashley Bloomfield, called it a ‘‘significant mark in our journey’’.
Testing at the border was introduced the next day, and within a week new cases began to be detected.