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ANALYSIS: A new case was enough to force Auckland back into lockdown less than a week after it returned to Level 1. Marc Daalder explains why
New Zealand has dealt with nearly a dozen border failures and minor community outbreaks of Covid-19. Only a couple have led to an escalation of the alert level, including the discovery of three new cases in the community on Valentine’s Day.
The latest outbreak was seen as a “false alarm” by some and Auckland left Level 3 a few days after the shutdown began. So why did the identification of a single new community case, probably linked to the Valentine’s Day group, require a return to Level 3?
In the end, it was uncertainty that drove the decision. The exit from Level 3 on February 17 was criticized by public health experts because too much was still unknown. How had the outbreak started? Were there still undetected cases in the community?
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Abigail Dougherty / Stuff
Cars and walk-ins line up for Covid testing outside Papatoetoe High School in Auckland during the first three-day Level 3 shutdown after three cases were found in the community on February 14 (File Photo )
“Not having identified the source leaves us with: Are there undetected strings [of transmission]? “Asked the University of Auckland Siouxsie Wiles the day before Auckland left the lockdown.
“The details of today’s case are too disturbing” not to return to the lockdown, Wiles said Saturday.
In the days since, three separate families connected to Papatoetoe High School have returned positive tests, including new cases identified Saturday night. Two of these families had no clear link to the so-called Case A of the Valentine’s Day group, which had attended school while infected on February 10.
The case found Saturday afternoon, labeled Case M by health officials, is particularly concerning. They are siblings of a student at Papatoetoe High, but that student has tested negative three times and has not shown any symptoms so far. That raises the possibility that Case M was not infected by his brother, but by someone else in the community. It is possible that this theoretical undetected spread was recently detected.
“It is not impossible that someone [with Covid-19] test negative three times, but it is unusual. Therefore, it is possible that the infection has come through another route and that may mean that there is another group of cases in the community, linked to the school or otherwise, “said Covid-19 modeler Shaun Hendy.
Health Director General Ashley Bloomfield said transmission from high school remained the most likely source of Case M’s disease, but the lack of certainty led to escalating alert levels.
Ross Giblin / Stuff
Jacinda Ardern and Ashley Bloomfield call a late night press conference on Saturday to announce that Auckland will move to alert level 3 and the rest of the country to level 2.
Another worrying aspect of the new case is the possibility that they have been spreading the virus in the community for the better part of a week. Bloomfield said the person first developed symptoms on Tuesday and that the general rule of thumb for Covid-19 is that people are infectious for 48 hours before symptoms appear. While, as a family contact for a Papatoetoe High School student, Case M was required to isolate himself at home during this period, contact tracing has revealed that they did, in fact, visit several high-risk locations.
These include a gym, a supermarket and the Manukau Institute of Technology, where the case takes classes.
Even with the original Covid-19 variants, people infected last weekend or early in the week could have been infectious on Friday or Saturday. Evidence is also emerging that the new, more transmissible Covid-19 variants have a shorter average period between when someone becomes infected and that person can transmit the virus to others.
“This may mean that there are currently subsequent cases in the community that are also infectious,” Hendy said.
We know that the Valentine group involves variant B.1.1.7 first identified in the UK. That throws another wrench into the works. In addition to the shorter incubation period, the variant is more transmissible, as experts say Level 3 restrictions may have a difficult time containing a widespread outbreak of B.1.1.7.
Analysis of B.1.1.7 transmission abroad indicates that it is spreading 30 to 70 percent more than the variants of the virus we are used to. The assessment of the Level 3 lockdown in Auckland in August found that the breeding number, the average number of people infected by a given case, dropped to 0.7. That means the new variant could see a breeding number of between 0.91 (in which it would take weeks to reduce the cases to almost zero) and 1.19 (in which the cases would increase despite the restrictions).
Newsroom.co.nz/Supplied
How fast the B.1.1.7 strain of Covid-19 could spread.
Given the combination of factors, a more communicable variant spread by a person who visited numerous high-risk locations during the past week, while the source of his own infection remains unclear, the government made the prudent decision to return to confinement. We can only hope that we have not acted too late.
