As the Delta variant and four more cases are confirmed in the community on Wednesday morning, Marc Daalder says ministers face key questions
ANALYSIS: New Zealand is back at Level 4 for the first time in 16 months.
The trigger was the discovery of a case of Covid-19 in the community that is infected with the Delta variant of the virus.
The case, a 58-year-old man from Devonport in Auckland, is considered to have been infectious from Thursday. He and his wife (fully vaccinated, tested negative) travelled to the Coromandel over the weekend, returning on Sunday.
Given that he crossed between regions, that he attended crowded venues like a pub on a rugby test night, and that he's been infectious for five days, the Government is considering the situation a national issue. Hence, the nationwide return to Level 4 - though the light is at the end of a shorter tunnel for those outside Auckland and the Coromandel, who are at this stage only scheduled to be at the highest alert level for three days.
Four additional people have since returned positive test results. One is a co-worker of the Devonport man and the other three are that co-worker's close or household contacts. Jacinda Ardern has also confirmed the virus genome is a match with Delta.
Still, so much remains unknown about the situation. Officials are rapidly working to trace and isolate the man's contacts, discover the origin of his infection, and sort out a slew of other issues. Here are the key questions that ministers will be asking as they figure out what the next steps will be.
Where did it come from and how big is the upstream outbreak?
With the confirmation of four further cases Wednesday morning, there still remains the question of which or who is the case that could point to this outbreak's origin. Because the man has no direct association with the border or MIQ, he must have been infected by someone else who is currently in the community.
The best-case scenario here is that he was infected by someone who works at the border or in MIQ, or who has recently exited MIQ. That would imply the outbreak is relatively contained - this one person may have infected a few others and there's still the Devonport man's own onward transmission to worry about, but this timeline wouldn't allow for an outbreak with triple digit cases.
Of course, we may never learn the answer to the first part of this question. In Auckland's last August outbreak, the exact source of the border breach was never found. That in itself was indicative of a larger outbreak - and we did indeed end up with more than 150 cases, including dozens who had been infected before the discovery of the cluster.
It is entirely possible there are several upstream chains of transmission, each of which may have infected an average of five to nine other people, or even dozens in the event of a super-spreader.
Modelling done after last year's second outbreak found that, if a third of people with symptoms get tested, any outbreak is likely to involve no more than 50 cases at the time we find it.
Delta changes the maths on that, making outbreaks larger, but vaccinations mean the percentage of people who need to get tested drops too.
Te Pūnaha Matatini has more recently modelled a variety of scenarios with viruses that are more or less transmissible and the population at different levels of vaccination. With a variant as transmissible as Delta and with a population only 20 percent fully vaccinated, experts found that if 15 percent of symptomatic people are getting tested, the median outbreak size would be around 75 cases.
However, the error bars on that figure are large - the true number could be as low as 20 or as high as 150.
That 15 percent testing figure is about where we've been over the past few weeks, according to data from Flutracking.net.
Are you feeling lucky?
One of the most important and least well understood traits of the coronavirus is a phenomenon called overdispersion. In short, with the coronavirus, a small number of people are responsible for the vast majority of cases. And most cases don't pass the virus on to anyone at all.
That's how the Northland case managed to take a road trip but not infect her husband. It's how a man in the February outbreak was able to visit the gym and go to university while infectious but not transmit to anyone else.
This trait is still a feature of Delta, but the percentage of people who don't infect anyone else appears to be smaller than in the original coronavirus. By coincidence, on Tuesday morning I wrote about this crucial mechanism and how differences with Delta change the game.
There's still a decent chance that the Devonport man infected no one or just one or two people. That his wife tested negative doesn't tell us much, as her two doses of the Pfizer vaccine will have drastically reduced her chances of becoming infected either way. And his co-worker testing positive could mean the co-worker infected him or vice versa.
On the other hand, we could be unlucky and be about to face the full force of the Delta variant. On average, people with Delta infect between five and nine others - compared to just 2.5 others with the original coronavirus. But when the circumstances allow, some can be outliers - that's the overdispersion - and infect dozens of others.
Certainly the circumstances allow for such super-spreading in the case of the Devonport man. He attended a crowded pub on Saturday night, when the All Blacks were playing. He also visited a number of other hospitality venues while on vacation, allowing for further super-spreading. And his tourist activities would have exposed people from potentially all over the country, who may well have returned home by now.
In other words: He may have infected no one, or he may have infected hundreds.
How long will Level 4 last?
The answer to this is dependent on the answer to the two previous questions.
If we find a close link to the border (meaning limited upstream transmission) and we're lucky on the downstream transmission, then this could be wrapped up pretty quickly. Cases can be isolated, their contacts traced and isolated, rinsing and repeating until everyone who tests positive has been isolated the entire time. That allows for a steady progression down the alert levels - and perhaps an earlier descent for those parts of the country where no cases are found.
However, the discovery of four new cases makes this scenario a bit less likely. It remains to be seen whether the co-worker was infected by the Devonport man and went on to infect his own household contacts, or whether he may have been the source of the Devonport man's infection. Either way, at least one person has been shown to be able to spread the virus to a number of others, meaning the scope of the outbreak is less likely to be tightly contained.
The worst-case scenario is quite a lot worse. If we never find the source but find a cluster in Auckland that predates the Devonport man's infection, as well as a new nationwide cluster originating in the Coromandel, we might find ourselves in Level 4 for some time. It took two-and-a-half weeks at Level 3 and another three weeks at Level 2.5 for Auckland to crush an outbreak of dozens back in August and September of last year. And that was the original variant of the virus.
This time, we have the stronger Level 4 measures at our disposal, but also a much more transmissible foe. If there are hundreds of cases already out there, a lockdown on the scale of the four-and-a-half weeks in March and April might be more appropriate. Of course, we also have vaccination on our side and a surge in first doses could further bolster our resilience to an outbreak.
The most likely scenario is somewhere in the middle. It's hard to believe we'll get lucky on both ends of transmission. If we're dealing with an outbreak the same size as Auckland's last year, we might be able to defeat it with a few weeks of Level 4 and then a longer period at Level 3.
There are two key things that people can do to help bring Level 4 to an end more quickly. First: Get tested if you have symptoms.
The more people are tested, the better our chances of finding every case. And if testing rates are high, the Government can have confidence it has a full view of the outbreak.
If we're finding relatively few cases but testing rates are low, the Government will (appropriately) be more cautious in stepping down alert levels, fearful of undetected pockets of transmission. In the same situation but where most of those who are symptomatic get tested, officials can more easily recommend removing restrictions. And if that added testing prompts us to find new cases, the extension of restrictions will be shorter in net terms than the consequences of yo-yoing in and out of lockdown.
The second thing people can do: Follow the rules. Stay home, wash your hands, don't let your bubble intermingle with another one.
We know Level 4 works. But that requires us to actually do what is asked of us. It won't be easy, but it's how we protect our friends and families and communities.
