Scientists say the Delta variant of the Covid-19 virus could still be lurking among us, and are backing the government's decision to extend restrictions in Wellington.
Wellington's Taranaki Street Covid-19 testing site. Photo: RNZ / Dom Thomas
If anyone was infected on Sunday or Monday, now is around the time they would most likely develop symptoms.
The capital is reaching the crunch point, when anyone who contracted the Delta variant last weekend would be most likely to develop symptoms, University of Canterbury maths and modelling expert Professor Michael Plank said.
He is pleased alert level 2 has been extended, and said it was now a waiting and vigilance game.
The NSW traveller who has since tested positive for the Delta variant was in Wellington from 18 to 21 June. But his partner who travelled with him has only just returned a positive result for the virus on her second test.
"It's essential you stay alert for symptoms," Plank said in a statement.
"If there is even one case lurking out there, it has the potential to spread like wildfire because the Delta variant is so infectious and our vaccination coverage is too low at the moment to slow it down much.
"New South Wales has one of the best contact tracing systems in the world, but it hasn't been able to keep up with the speed the virus is spreading."
By yesterday 2067 of 2444 identified potential contacts of the man had been tested in New Zealand, and all results so far have come back negative.
However, as with the man's partner, the virus can sometimes not show up in the tests early in an infection. And the timing of the partner's result indicates the Sydney man was infectious while here.
So, even after a negative test, all contacts have been asked to stick to the particular instructions they have been given, including isolating, retesting, watching for symptoms and reporting any symptoms that do show up.
And the higher the testing rates go, particularly in Wellington, the more confidence authorities can have to relax the alert levels sooner.
Epidemiologist Nick Wilson said Wellington may not have turned up any cases so far - and may have "dodged a bullet, but we can't relax yet".
"The NZ government has made a wise decision to keep at the current alert level 2 settings for Wellington for at least a few more days given the major problems being caused by the new Delta variant in Australia," Wilson said in a statement.
He said now was the time for the government to upgrade fortifications, by ensuring all frontline border and healthcare workers have been vaccinated as well as including masking for indoor venues in the alert level system and making it compulsory to scan in with the Tracer app at high risk indoor venues.
Another epidemiologist, Professor Michael Baker, said the extension was "fully justified", as the numbers of people potentially exposed had the potential to trigger a "super-spreader event" if full precautions are not taken to stop potential transmission.
"Given the timing, it is possible that some of these contacts are still incubating this infection and will only be identified in the coming few days, though the risk is now low," he said in a statement.
Baker told RNZ earlier today that several gaps still exist in the precautions, including compulsory QR code scanning for large venues and a high level of indoor mask use. He said the pause in the quarantine-free trans-Tasman bubble gives us the chance to reassess it.
University of Otago healthcare senior lecturer Lesley Gray said the alert level 2 extension was "reasonable".
She wants pre-departure testing to be introduced for anyone travelling to New Zealand without quarantine.