Wait and see for South: scientists

Alert Level 4 is the right place for the South Island to be right now, but a shift to Level 3 or lower later this week is feasible if high test rates continue to show no Covid-19 cases, scientists say.

Prime Minister Jacinda Ardern announced yesterday that New Zealand will remain at Level 4 until at least 11.59pm on Friday, and said Cabinet would consider later in the week whether regions without cases of Covid-19 might drop down from full lockdown.

Auckland, the centre of the outbreak, will definitely stay at Level 4 until early next week and quite probably well beyond.

"We don’t yet believe we have reached the peak of this outbreak, or necessarily the edges of it," Ms Ardern warned.

"Cases may continue to get worse before they get better and I know we are all prepared for that."

More than 14,000 close contacts have been identified so far nationwide.

Last night, the Ministry of Health said 135 of those people were in the South Island, and 50 were isolating in Otago and Southland, the Southern District Health Board regions.

University of Otago public health physician Prof Nick Wilson said there was still considerable uncertainty about the outbreak, but early indications were that there had been no super-spreader events before New Zealand went into lockdown.

However, considerable planning and a high rate of testing would be needed before areas such as the South Island scaled back from Level 4, he said.

"Also, more work is needed on allowing for a strong regional approach with tight internal border controls.

"This will allow for regions such as the South Island that might soon be declared Covid-19-free (after more testing in the community and of wastewater) to move down through the alert levels faster than regions that still have cases."

University of Canterbury mathematics modeller Prof Michael Plank said given the incubation period for the Delta variant was a week or more and the outbreak was six days old, there was a compelling argument for the South Island to remain at Level 4.

"By Friday we will know more and a drop to Alert Level 3 is a realistic possibility for regions with no active cases."

South Island wastewater tests having returned negative results was a good sign, Prof Plank said.

"The list of locations of interest keep increasing and thousands of people will have visited them, and it is quite likely that people from the South Island could have visited those locations.

"We know how much people like to move around the country, so we really have to wait and see."

Wastewater is regularly tested in Christchurch, Dunedin, Invercargill and Queenstown, and late last week Wanaka was added to the schedule.

For the South to drop back from Level 4 would take solid testing numbers, all of which were negative, and anyone with cold and flu symptoms getting tested, Prof Plank said.

University of Otago epidemiologist Prof Michael Baker said it was entirely possible people from the South Island had contracted the virus and every effort should be made to ensure that any southern cases were detected.

"Our lockdown is much more robust than what we have seen in New South Wales, which is great and makes contact tracing much less critical because virtually everyone is in quarantine, but essential workers still have to leave the house so you cannot entirely rely on that," Prof Baker said.

"It is always wise to act with caution."

High volumes of testing and extensive wastewater testing should give an idea if the disease was in the South Island relatively quickly, he said.

"If in a two-week period you didn’t see any cases you would feel a great deal more assured."

mike.houlahan@odt.co.nz