When Cabinet meets at 3pm today to review whether Auckland should remain at Level 3, it will have a lot to consider.
First, the good news: Since the discovery of three new community cases of Covid-19 on Sunday, no new cases have been reported. More than 6,000 people in Auckland have been tested for the virus and none have come back positive. That includes 33 people who are considered close contacts of the Papatoetoe family.
Then there’s the bad news, and it’s quite a bit longer. Most of it, however, comes down to uncertainty – we still don’t know how the family was infected, we still don’t know whether some close contacts might have been infected and we still don’t know whether there might be other undetected community cases out there.
Plus, there’s the fact that the infection is a new, more transmissible variant of Covid-19 which might require Level 4 measures to contain in the event of a widespread outbreak. Not to mention the discovery of two new cases of Covid-19 in the community on Wednesday, both students at Papatoetoe High School.
Add it all up and the case for extending the current settings through the weekend is strong, experts say.
Close contacts
Health officials have identified 109 people who could be considered close contacts of one of the three community cases. While 33 of these people had returned a negative result by this afternoon, two-thirds were still waiting for their tests to be processed or waiting for a test in the first place.
Covid-19 Response Minister Chris Hipkins told a select committee today that more tests of close contacts had come back since, including the positive result for a Papatoetoe High School student and their sibling. Other results were still outstanding, he said.
That makes it difficult to say whether onward spread of the virus has been contained, University of Auckland microbiologist Siouxsie Wiles said. Even those who have tested negative could be still incubating the virus – the PCR tests used in New Zealand are best at detecting an infection just prior to symptom onset and after someone has developed symptoms.
In fact, the Ministry of Health’s locations of interest webpage asks people who may have been exposed more recently – for example at one of three South Auckland Bunnings Warehouses – to isolate at home and only get tested on February 18, because a test might not detect any virus prior to that date. A decision to move down alert levels would mean casual contacts would be getting tested for the first time on Thursday, after restrictions were lifted, and their results would likely only come back on Friday.
“Do we delay a couple more days so we’ve had a week of obstruction, but it essentially then gives us until Sunday and it gives us a huge amount more data, or do we move, we allow movement of people again and then if something pops up it will have had more opportunity to spread?” Wiles said.
“This is the most frustrating thing, that while we’ve had two days of no positives – that’s a great sign – we’re still very much in that incubation period.”
However, it helps that the 109 close contacts will be isolated and not moving around the community, even if restrictions are lifted.
“If they’re isolated, the risk of further transmission is minimised. Although that also depends on what that isolation looks like and whether they’re isolating with their close contacts also isolated. At least with the change in alert level, most of those people are at home, in their bubble,” Wiles said.
Source investigation
Wiles says it’s reassuring that the close contacts have been effectively traced and isolated and will hopefully be returning test results rapidly as well.
“At least the stuff we know about is essentially contained.”
But what about the stuff we don’t know about?
We still don’t know how the family was infected in the first place. While the mother’s occupation doing laundry for aircrew at Auckland Airport seems to be the most likely vector, the daughter developed symptoms prior to her mother. Wiles says it’s possible that the mother became infectious and infected her daughter but then took longer to develop symptoms, but that officials were still being prudent in investigating Papatoetoe High School as a potential source.
Understanding the source of the infection is key because that source could have infected others as well.
“Not having identified the source leaves us with: Are there undetected chains [of transmission]?” Wiles asked.
Covid-19 has to have come from somewhere. So long as there’s a missing link in the chain of transmission, there’s the possibility of other missing cases out there – entire missing chains.
Finding those is a lot more difficult than finding onwards transmission from the family of three, when the places they’ve been are known and the people they’ve interacted with are categorised as close contacts.
One of the new tools the Government is relying on to find any potential transmission from the missing link is testing of wastewater. This method could help identify whether there are any other cases of Covid-19 in the community. If wastewater testing finds something, then a more targeted search could be implemented.
Shaun Hendy, who leads the pandemic modelling project at Te Pūnaha Matatini, said wastewater testing could be crucial to informing the Government’s decision today.
Otherwise, we simply have to rely on people who develop symptoms coming in to get tested. But because Covid-19 can take up to 14 days to show symptoms, we’re still well within the incubation period for any potential undetected cases. No new positive tests so far is a good sign, but it doesn’t rule out the possibility of a positive test in the near future.
Level 2 or Level 3? Maybe Level 2.5?
It is this uncertainty around possible undetected transmission that drives Wiles to recommend remaining at the current alert levels through the weekend. If no new cases are found today or over the next four days, then Auckland could step down with much more confidence that there isn’t undetected transmission. But as it stands, we’ve only had two days of mass testing and labs are still ramping up their capacity to process tests.
Although some 15,000 tests were taken nationwide on Monday, including more than 10,000 in Auckland, fewer than 6,000 were processed. For all we know, there could be unprocessed positive results among the remainder, or among the thousands of swabs that were taken Tuesday.
“It feels very positive but it also is frustrating because we don’t have huge amounts more information than we did. It just feels like we’re still in that slightly too early to say and there’s still lots more tests to come back,” Wiles said.
“Do you behave more cautiously in order to [prevent] what could be something quite big next week?”
Hendy is more comfortable with a potential decision to move down.
“When the decision was made on Sunday, this was looking a lot like the Auckland August cluster. From everything we knew on Sunday, that looked like the scenario we were dealing with. But over the next couple of days, we haven’t found other cases. That’s very different from what we saw in August, when we quite rapidly started to see other cases associated with the cluster. I think that and the wastewater testing will actually give them quite a bit of confidence going into that decision tomorrow,” he said.
“Should we start to see cases among those close contacts, a significant number of those turning up positive, then that might make Cabinet want to be more cautious. But at the moment I think they’ll be feeling reasonably confident that we’re not looking at another Auckland August scenario. That being said, it is one of the new, more transmissible variants. That probably means we should be cautious.”
Michael Baker, a University of Otago epidemiologist who has advised the Government on its response, agreed with Wiles that retaining the current levels would be the “most cautious” approach. As an alternative, he suggested the possibility of a Level 2.5, where mass masking would be mandated and high-risk, super-spreading venues like bars and nightclubs would remain closed but low-risk workplaces could open.
If the rest of those tests of close contacts come back negative, it’s really telling us we’ve got something quite different from that Auckland August outbreak.
