The latest outbreak began with a 58-year-old man in Auckland, New Zealand’s biggest city, on Tuesday.
New Zealand announced two new cases, bringing the total to seven. One of the cases involves a nurse at Auckland Hospital, which had been placed in “internal lockdown” while all staff and patients are tested.
The island nation has avoided the worst of the pandemic with strict border control and a strategy of elimination. The nation of five million has recorded only 26 deaths from the disease.
Ardern said she was confident the strategy would succeed against the highly transmissible Delta strain.
“Yes, Delta poses a greater threat, but the same tools that have worked before will do so again if we follow the rules,” she said.
Ardern imposed a nationwide three-day lockdown after the first case emerged.
Auckland and nearby Coromandel, where the man had travelled to before he was diagnosed with the disease, will be under restrictions for at least a week as health authorities work to find the source of the infection.
Wastewater testing in the city had detected no sign of the virus, giving cause for optimism.
“That tells us that, if we have something, it doesn’t appear to be a longstanding outbreak because we haven’t had anything in our wastewater testing,” she said.
New Zealand’s vaccination programme has been slower than many other developed nations despite a recent acceleration. About 32 percent of people have had at least one dose of the vaccine while 18 percent are fully vaccinated.