(CNN) New Zealand's Prime Minister Jacinda Ardern has announced a nationwide lockdown after the country confirmed one coronavirus case -- the first locally transmitted Covid-19 case in the community since February.
Ardern told a press conference Tuesday authorities were assuming it was the contagious Delta variant, although genome sequencing is still underway.
An unvaccinated 58-year-old man in the country's largest city Auckland tested positive for the virus. The man had traveled to other parts of the country, and had no obvious link to the border, Director General of Health Ashley Bloomfield said Tuesday.
New Zealand will be under the strictest level lockdown level for the next three days starting from 11:59 p.m. Tuesday, local time, Ardern said. Under level four lockdown, everyone must stay home and businesses are closed aside for essential services such as supermarkets and pharmacies.
New Zealand was last under its most serious lockdown level a year ago, Ardern said.
Auckland and the Coromandel Peninsula -- an area of the country's North Island where the patient traveled -- are likely to be under a level four lockdown for a week.
"We are one of the last countries in the world to have the Delta variant in our community," Ardern said. "We're in the position to learn from experience overseas, and what actions work, and what actions don't work."
"Delta has been called a gamechanger -- and it is. It means we need to again go hard and early to stop the spread. We have seen what can happen elsewhere if we fail to get on top of it. We only get one chance."
New Zealand has been praised for its handling of the virus, which saw it close borders to almost all foreign nationals early, and impose strict state-run quarantines on incoming travelers.
That approach has seen it avoid the devastating outbreaks seen in other countries, and, prior to Tuesday's announcement, life in the country had largely returned to normal. New Zealand has reported fewer than 3,000 Covid-19 cases and only 26 deaths in a population of about 5 million.
But New Zealand has been slow to vaccinate. According to data collated by CNN, New Zealand has fully immunized less than 20% of its population.
Neighboring Australia, which was also previously praised for its handling of the virus, has been battling its own Delta outbreak for the last few weeks. More than half of Australia's population are in lockdown -- and the country's most populous city Sydney has been in lockdown since June.
Earlier this month, New Zealand announced plans to begin reopening its doors to vaccinated travelers from low risk countries from early 2022, signaling a tentative relaxation of strict pandemic border controls.
CORRECTION: An earlier version of this story misstated the location of the confirmed case. He does not have obvious links to the border.