A man in his 30s turned up at hospital on Friday with symptoms. He’s now in ICU. Nobody knows how he contracted the virus.

Amid the daily rush of numbers as Auckland’s tally of active Covid-19 tops 110, one new infection has given Ashley Bloomfield particular pause for concern. It’s another indication that the growing cluster in New Zealand’s largest city still hasn’t been fully contained.

On Friday evening a man in his 30s showed up at the North Shore Hospital emergency department. He hadn’t been tested earlier for Covid-19 but had serious symptoms on arrival. The man is now in critical condition in the intensive care unit.

“The concern is, if the first time you find out about a case is when someone presents to hospital, that’s a little yellow flag. That means the person has been infected for a few days,” the director general of health told reporters today at the Beehive.

The man’s family and work contacts have been identified by contact tracers and all that have so far been tested have returned negative tests. The genome of the man’s infection has been sequenced and linked back to the large Auckland cluster – now the largest New Zealand has seen – related to Americold cool storage company.

However, the genomic comparison apart, no link has yet been made between the man, his contacts and anyone in the wider cluster. It still isn’t clear how he got infected. The man’s health condition has not hindered contact tracers during the sometimes lengthy interviews they conduct as they try to reconstruct a person’s movements over weeks, according to Bloomfield.

Unlike some countries where high infection rates and less accessible health care systems mean very sick people show up at hospital, this case is rare in New Zealand. With the widespread availability of free Covid-19 tests here, most community cases have been detected during symptomatic testing or when testing close contacts of positive cases.

Apart from the man in his 30s, there are currently seven more people in the country in hospital, with two more in ICU. There are 129 cases in total, of which 19 were detected at managed-isolation facilities at the border.

Of the 110 active community cases in the country, one is a maintenance worker at a managed-isolation facility who is believed to have been infected after picking up the virus from a surface in an elevator shared with returnees. Most of the remaining 109 have been linked to the wider community cluster. Those infections have largely been within families or workplaces, although some cases are thought to have picked up the virus during shopping or from riding a bus after a stranger with Covid-19 disembarked.

Bloomfield was unable to provide the exact number of cases that haven’t been “epidemiologically linked” back to the cluster, but even a small handful of such cases “gives us pause for thought,” he said. These unlinked cases were an important part of Bloomfield’s reasoning yesterday when he told cabinet that it should extend Auckland’s lockdown, he said. The cases are also the reason why the government wants to keep testing rates high. The health minister announced that he’d like to see 70,000 tests over the next week.

Chris Hipkins said the perimeter of Auckland’s main cluster hasn’t yet been fully identified. However, each new case linked to it through genomic testing or epidemiological work has helped officials identify what they are facing.

“It’s like trying to assemble a jigsaw puzzle and each new piece of the puzzle provides you with more information,” said Hipkins. “There are still some gaps in the jigsaw at the moment, which is very clear because we haven’t quite identified with any certainty the origins of this cluster yet.”

Health investigators are still trying to pinpoint how the virus arrived back in the community, but so far none of their hunches have panned out. Early concerns that Covid-19 might have hitchhiked back into New Zealand on refrigerated freight now has been dismissed following environmental testing at a south Auckland warehouse. Widespread testing at the country’s border facilities and ports has also not revealed any source of infection linking the Auckland cluster with the wider world.