Three cases of Covid-19 in the community have now been confirmed in Wellington.
But Te Pūnaha Matatini Covid-19 modeller Professor Michael Plank said it was "somewhat reassuring" that the Wellington cases had visited an Auckland location of interest and so appeared to be linked to the main cluster.
There are 11 new Covid cases, including the three in Wellington - and level 4 lockdown is set to be extended nationwide until at least early next week.
"However, it also shows how easily the virus can be transported around the country," he said.
"The fact that 149 contacts have been identified outside Auckland suggests there is a high risk that the virus may have spread to other regions too, including potentially the South Island."
Plank said many people from across the country would have been visiting Auckland before the lockdown and subsequently travelled home.
"These people could still be in their incubation period and so may not develop symptoms and get tested for a few more days," he said.
"There is a high chance this is now a national outbreak and so the national lockdown needs to continue for the time being."
Of the 11 new cases, eight are in Auckland and three are in Wellington. The three in Wellington had recently travelled to Auckland and visited a location of interest there.
Nineteen cases are now confirmed as part of the Auckland outbreak, with the remaining 12 under investigation to confirm the linkage to the outbreak. Initial assessment shows in most cases there is a plausible link.
In Auckland, thousands of secondary school pupils, their families and staff are now under isolation orders after more Covid cases among teenagers emerged overnight.
The news of the Wellington cases came after a new case was confirmed in Auckland this morning - a man who had been receiving hospital care at North Shore Hospital earlier in the week.
They were among about 120 staff at the hospital who were rostered on and likely in the affected areas at the same time as the patient.
The 30 staff had since been stood down and extra staff were now being sourced from outside the region to help manage demand.
Testing is being set up at the hospital for affected staff.
As for patients, there were approximately 107 in the affected areas at the same time as the positive patient.
Of these, 29 remain admitted as inpatients and were being isolated and tested for Covid-19.
Seventy-eight have been discharged and are self-isolating at home. Public health officials were keeping in touch with them.
Patients needing emergency care were now being diverted from North Shore Hospital to other emergency departments across metro Auckland for the time being.