It’s been reported around the world: New Zealand went into lockdown after a single case of Covid-19 in Auckland.

But as case numbers climb, and with fewer than 1 million Kiwis fully vaccinated, experts are convinced it was the right decision.

On Tuesday afternoon, the Ministry of Health said officials were investigating a new case of Covid-19 in the community, dubbed Case A.

That evening, Prime Minister Jacinda Ardern announced a nationwide alert level 4 lockdown for at least three days from midnight. Auckland and the Coromandel, where the infected person recently visited, would be in lockdown for seven days.

Overnight, the ministry confirmed the first case detected – a 58-year-old tradesman who lives in Devonport, on Auckland’s North Shore – had been infected with the Delta variant of the virus.

By 9am on Wednesday, four new cases had been announced, including a 20-year-old tradesman, an employee of Case A.

All four – two men and two women – lived together in a flat on Auckland’s North Shore. It’s been reported the women are sisters; one is a nurse at Auckland Hospital, the other a teacher at Avondale College.

On Wednesday afternoon, another two cases were announced – both referred to as friends of the North Shore flat.

While genome sequencing of the original case showed a link to the New South Wales outbreak in Australia, it’s not yet known exactly how the virus spread to the Aucklanders.

“We are absolutely anticipating more cases,” Ardern said.

On Wednesday evening, the Prime Minister’s Office announced three additional cases, bringing the total number of community cases to 10.

One was an Air New Zealand crew member who tested positive after travelling from Japan to Auckland. The woman, in her 60s, doesn’t appear to be linked to the current community outbreak.

Among the cases was an Auckland University of Technology student. They attended a lecture on Tuesday, with 84 other people.