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The Government is rightly taking a precautionary approach to the nerve-wracking news of four community transmission cases of Covid-19.
Mass testing - 50,000 tests by the end of the week - is being rolled out in Auckland and around the country to gather as much information as possible about the extent of the outbreak.
The best-case scenario, as Professor Michael Baker says, is that the source of transmission is found and all possible branches of transmission are quickly ring-fenced.
It's possible, however unlikely, that there are very few new cases and alert levels can be eased soon.
But the man in his 50s in the Covid-infected family had strong symptoms for five days before being tested. He and his partner went to work while symptomatic, and sick family members travelled to Rotorua and visited tourist sites over the weekend.
That's a long time and several places where new chains of transmission could have been triggered.
It's almost certain there will be more cases, and they may already be all over the country, given the travel freedom we have been enjoying.
Consider also that people can be infectious for days before showing any symptoms. In April, the World Health Organisation said "people can test positive from one to three days before they develop symptoms".
In July, the WHO said: "Transmission can occur from people who are infected and remain asymptomatic, but the extent to which this occurs is not fully understood and requires further research as an urgent priority."
Erring on the side of caution, then, is to be prepared for the restrictions - in Auckland and for the rest of the country - to be extended beyond midnight Friday, and even tightened further.
And if the Blues-Crusaders game went ahead in Auckland on Sunday, it would beggar belief.
Another key fact is the incubation period, which can be up to 14 days. That's why the Government has rightly prepared New Zealand for lockdown in two-week blocks.
It doesn't mean that Auckland will be in lockdown lite for at least two weeks, but it would come as no surprise if that turned out to be the case.
A worst-case scenario is if dozens of transmission chains are already spreading over the country, in which case a quick return to lockdown is the only credible course of action.
But there is a reason to be optimistic. Prime Minister Jacinda Ardern has rightly pointed to the absence of overwhelmed hospitals as a sign that this outbreak hasn't exploded.
Did the ministry drop the ball?
Key questions remain about the source of infection and whether the chain of transmission could have been detected earlier.
It's unclear if the Ministry of Health dropped the ball. Testing numbers have fallen off a cliff since the end of June, when the ministry changed the case definition - if you didn't meet the "higher index of suspicion", you were unlikely to be tested.
Public health advice is for 4000 tests a day to ensure confidence about the prevalence of Covid-19 in the community. That has only been achieved four times since the end of June.
And it's not just about the number. The source would have come from overseas, so it makes perfect sense for the Government to test the 6000-7000 people who work at the border or in managed isolation or quarantine (MIQ) facilities.
Ministry data on testing these workers has not been forthcoming, even though it was one of the first things Health Minister Chris Hipkins asked for when he took over from David Clark.
Public health experts have been calling for this kind of testing breakdown for months.
The Herald has repeatedly asked the ministry for daily testing numbers of these workers for three weeks. No answer.
Only today has Arden shed a smidgen of light on the matter - that workers at Auckland's Jet Park Hotel, where positive cases are quarantined, are tested more regularly than other MIQ workers.
It's possible - though can never be known - that higher rates of testing could have detected the transmission chain that infected the Auckland family earlier.
It's not just about the ministry, though. People were also refusing to be tested, leading to the Government's plea to "say yes to the test".
On the days where daily testing numbers topped 4000, pop-up testing stations were used. There is a clear case that they should have been used earlier, and should be used regularly from now on.
We will now see if the contact-tracing system really is gold-standard. It is certainly much improved since March, when chronic under-resourcing of public health units had left them unprepared for Covid-19.
Taiwan has showed us how an efficient contact-tracing system can allow a country to avoid a harsh lockdown, even if the outbreak is much wider than hoped.
The Herald asked the ministry - on June 12 - for the latest data on the average time taken for the end-to-end contact-tracing process (from first symptoms to 80 per cent of close contacts being isolated).
The ministry, which has published other metrics but not the end-to-end average time, has told us repeatedly that the information is not available yet.
Information issues have plagued the ministry throughout the Covid response.
Robust, timely and transparent information is vital to the Covid response. One can only hope the ministry will be more forthcoming about key data.
And that Ardern's team is not as information-deprived as the rest of us.