WELLINGTON (AFP, REUTERS) - New Zealand reported a breakthrough on Thursday (Aug 19) in tracing the source of a Covid-19 outbreak that plunged the nation into lockdown, with Prime Minister Jacinda Ardern saying it should help "stamp out" the virus.
Health officials have been trying to determine how an Auckland man contracted the coronavirus this week, ending a six-month run of no community cases in New Zealand.
Tests showed the man had a version of the Delta strain found in Australia, and Ms Ardern said investigations narrowed down the origin to a person who arrived from Sydney on Aug 7.
She said the traveller had been in quarantine and hospital since touching down, indicating the virus had not been in the community as long as initially feared.
"We believe we have uncovered the piece of the puzzle we were looking for," Ms Ardern told reporters.
She said finding the outbreak's source also increased the "ability to circle the virus, lock it down and stamp it out".
Case numbers grew by 11 overnight to a total of 21, she said.
Ms Ardern ordered a three-day national lockdown - New Zealand's first in 15 months - when the first case emerged on Tuesday, with Auckland and nearby Coromandel facing restrictions for a week.
"We're all prepared for cases to get worse before they get better, that's always the pattern in these outbreaks," she said.
But she said there were grounds for cautious optimism "because we believe it wasn't here for long before it was found".
The infected traveller arrived from Sydney on a so-called "red zone" flight, arranged to bring back New Zealanders stranded when Wellington suspended a trans-Tasman travel bubble due to multiple outbreaks in Australia.
The person tested positive two days later and was hospitalised a week after that.
Officials said it was still unclear how the virus spread into the community and 1,000 close contacts of positive cases were being assessed.
A decision is due on Friday on whether the three-day lockdown will be extended or end by Saturday.
The new cases may delay those plans and are causing concern in the nation, which has struggled to get its population vaccinated.
Only about 23 per cent of its 5 million people have been fully vaccinated, the lowest rate among the 38 members of the Organisation for Economic Co-operation and Development (OECD).
"It's no longer clear Jacinda Ardern's strategy is the right one," read one opinion piece in the New Zealand Herald.
Opposition National Party leader Judith Collins labelled the vaccination rollout as a failure.
Experts also said vaccinating everyone was the way to return to some normalcy.
"The virus is out there. We cannot go on thinking we will keep it out forever," said immunologist Graham Le Gros, Director of Malaghan Institute of Medical Research and Programme Director at Vaccine Alliance Aotearoa New Zealand.
"I think what is critical is that as a nation we now seriously focus on getting as many people vaccinated as possible, it is the only way our country can return to normality for the sake of our health and people's livelihoods."
Apart from some anti-lockdown protests, New Zealanders mostly followed rules and stayed at home.
'Covid zero' strategy
New Zealand has adopted a policy of eliminating the virus in the community, rather than containing it, which has resulted in only 26 deaths in a population of five million.
Neighbouring Australia has been pursuing a similar "Covid zero" strategy, but is struggling to contain outbreaks of the Delta variant.
Health authorities on Thursday urged mass Covid-19 testing for an entire Outback town in far western New South Wales, where an outbreak that began in Sydney two months ago is spreading.
The area is grappling with Australia's first significant outbreak in Aboriginal communities, with specialist military health teams deployed this week to boost sluggish vaccination efforts.
Early in the pandemic, Wilcannia's roughly 750 residents put up signs on the town's limits asking travellers not to stop, fearing the virus could obliterate an already vulnerable community where more than 60 per cent identify as Indigenous.